New Empirical Evidence: Students’ “Persistent Economic Disadvantage” More Likely to Bias Value-Added Estimates

The National Bureau of Economic Research (NBER) recently released a circulated but not-yet internally or externally reviewed study titled “The Gap within the Gap: Using Longitudinal Data to Understand Income Differences in Student Achievement.” Note that we have covered NBER studies such as this in the past in this blog, so in all fairness and like I have noted in the past, this paper should also be critically consumed, as well as my interpretations of the authors’ findings.

Nevertheless, this study is authored by Katherine Michelmore — Assistant Professor of Public Administration and International Affairs at Syracuse University, and Susan Dynarski — Professor of Public Policy, Education, and Economics at the University of Michigan, and this study is entirely relevant to value-added models (VAMs). Hence, below I cover their key highlights and takeaways, as I see them. I should note up front, however, that the authors did not directly examine how the new measure of economic disadvantage that they introduce (see below) actually affects calculations of teacher-level value-added. Rather, they motivate their analyses by saying that calculating teacher value-added is one application of their analyses.

The background to their study is as follows: “Gaps in educational achievement between high- and low-income children are growing” (p. 1), but the data that are used to capture “high- and low-income” in the state of Michigan (i.e., the state in which their study took place) and many if not most other states throughout the US, capture “income” demographics in very rudimentary, blunt, and often binary ways (i.e., “yes” for students who are eligible to receive federally funded free-or-reduced lunches and “no” for the ineligible).

Consequently, in this study the authors “leverage[d] the longitudinal structure of these data sets to develop a new measure of persistent economic disadvantage” (p. 1), all the while defining “persistent economic disadvantage” by the extent to which students were “eligible for subsidized meals in every grade since kindergarten” (p. 8). Students “who [were] never eligible for subsidized meals during those grades [were] defined as never [being economically] disadvantaged” (p. 8), and students who were eligible for subsidized meals for variable years were defined as “transitorily disadvantaged” (p. 8). This all runs counter, however, to the binary codes typically used, again, across the nation.

Appropriately, then, their goal (among other things) was to see how a new measure they constructed to better measure and capture “persistent economic disadvantage” might help when calculating teacher-level value-added. They accordingly argue (among other things) that, perhaps, not accounting for persistent disadvantage might subsequently cause more biased value-added estimates “against teachers of [and perhaps schools educating] persistently disadvantaged children” (p. 3). This, of course, also depends on how persistently disadvantaged students are (non)randomly assigned to teachers.

With statistics like the following as also reported in their report: “Students [in Michigan] [persistently] disadvantaged by 8th grade were six times more likely to be black and four times more likely to be Hispanic, compared to those who were never disadvantaged,” their assertions speak volumes not only to the importance of their findings for educational policy, but also for the teachers and schools still being evaluated using value-added scores and the researchers investigating, criticizing, promoting, or even trying to make these models better (if that is possible). In short, though, teachers who are disproportionately teaching in urban areas with more students akin to their equally disadvantaged peers, might realize relatively more biased value-added estimates as a result.

For value-added purposes, then, it is clear that the assumptions that controlling for student disadvantage by using such basal indicators of current economic disadvantage is overly simplistic, and just using test scores to also count for this economic disadvantage (i.e., as promoted in most versions of the Education Value-Added Assessment System (EVAAS)) is likely worse. More specifically, the assumption that economic disadvantage also does not impact some students more than others over time, or over the period of data being used to capture value-added (typically 3-5 years of students’ test score data), is also highly susceptible. “[T]hat children who are persistently disadvantaged perform worse than those who are disadvantaged in only some grades” (p. 14) also violates another fundamental assumption that teachers’ effects are consistent over time for similar students who learn at more or less consistent rates over time, regardless of these and other demographics.

The bottom line here, then, is that the indicator that should be used instead of our currently used proxies for current economic disadvantage is the number of grades students spend in economic disadvantage. If the value-added indicator does not effectively account for the “negative, nearly linear relationship between [students’ test] scores and the number of grades spent in economic disadvantage” (p. 18), while controlling for other student demographics and school fixed effects, value-added estimates will likely be (even) more biased against teachers who teach these students as a result.

Otherwise, teachers who teach students with persistent economic disadvantages will likely have it worse (i.e., in terms of bias) than teachers who teach students with current economic disadvantages, teachers who teach students with economically disadvantaged in their current or past histories will have it worse than teachers who teach students without (m)any prior economic disadvantages, and so on.

Citation: Michelmore, K., & Dynarski, S. (2016). The gap within the gap: Using longitudinal data to understand income differences in student achievement. Cambridge, MA: National Bureau of Economic Research (NBER). Retrieved from http://www.nber.org/papers/w22474

One Score and Seven Policy Iterations Ago…

I just read what might be one of the best articles I’ve read in a long time on using test scores to measure teacher effectiveness, and why this is such a bad idea. Not surprisingly, unfortunately, this article was written 20 years ago (i.e., 1986) by – Edward Haertel, National Academy of Education member and recently retired Professor at Stanford University. If the name sounds familiar, it should as Professor Emeritus Haertel is one of the best on the topic of, and history behind VAMs (see prior posts about his related scholarship here, here, and here). To access the full article, please scroll to the reference at the bottom of this post.

Heartel wrote this article when at the time policymakers were, like they still are now, trying to hold teachers accountable for their students’ learning as measured on states’ standardized test scores. Although this article deals with minimum competency tests, which were in policy fashion at the time, about seven policy iterations ago, the contents of the article still have much relevance given where we are today — investing in “new and improved” Common Core tests and still riding on unsinkable beliefs that this is the way to reform the schools that have been in despair and (still) in need of major repair since 20+ years ago.

Here are some of the points I found of most “value:”

  • On isolating teacher effects: “Inferring teacher competence from test scores requires the isolation of teaching effects from other major influences on student test performance,” while “the task is to support an interpretation of student test performance as reflecting teacher competence by providing evidence against plausible rival hypotheses or interpretation.” While “student achievement depends on multiple factors, many of which are out of the teacher’s control,” and many of which cannot and likely never will be able to be “controlled.” In terms of home supports, “students enjoy varying levels of out-of-school support for learning. Not only may parental support and expectations influence student motivation and effort, but some parents may share directly in the task of instruction itself, reading with children, for example, or assisting them with homework.” In terms of school supports, “[s]choolwide learning climate refers to the host of factors that make a school more than a collection of self-contained classrooms. Where the principal is a strong instructional leader; where schoolwide policies on attendance, drug use, and discipline are consistently enforced; where the dominant peer culture is achievement-oriented; and where the school is actively supported by parents and the community.” This, all, makes isolating the teacher effect nearly if not wholly impossible.
  • On the difficulties with defining the teacher effect: “Does it include homework? Does it include self-directed study initiated by the student? How about tutoring by a parent or an older sister or brother? For present purposes, instruction logically refers to whatever the teacher being evaluated is responsible for, but there are degrees of responsibility, and it is often shared. If a teacher informs parents of a student’s learning difficulties and they arrange for private tutoring, is the teacher responsible for the student’s improvement? Suppose the teacher merely gives the student low marks, the student informs her parents, and they arrange for a tutor? Should teachers be credited with inspiring a student’s independent study of school subjects? There is no time to dwell on these difficulties; others lie ahead. Recognizing that some ambiguity remains, it may suffice to define instruction as any learning activity directed by the teacher, including homework….The question also must be confronted of what knowledge counts as achievement. The math teacher who digresses into lectures on beekeeping may be effective in communicating information, but for purposes of teacher evaluation the learning outcomes will not match those of a colleague who sticks to quadratic equations.” Much if not all of this cannot and likely never will be able to be “controlled” or “factored” in or our, as well.
  • On standardized tests: The best of standardized tests will (likely) always be too imperfect and not up to the teacher evaluation task, no matter the extent to which they are pitched as “new and improved.” While it might appear that these “problem[s] could be solved with better tests,” they cannot. Ultimately, all that these tests provide is “a sample of student performance. The inference that this performance reflects educational achievement [not to mention teacher effectiveness] is probabilistic [emphasis added], and is only justified under certain conditions.” Likewise, these tests “measure only a subset of important learning objectives, and if teachers are rated on their students’ attainment of just those outcomes, instruction of unmeasured objectives [is also] slighted.” Like it was then as it still is today, “it has become a commonplace that standardized student achievement tests are ill-suited for teacher evaluation.”
  • On the multiple choice formats of such tests: “[A] multiple-choice item remains a recognition task, in which the problem is to find the best of a small number of predetermined alternatives and the cri- teria for comparing the alternatives are well defined. The nonacademic situations where school learning is ultimately ap- plied rarely present problems in this neat, closed form. Discovery and definition of the problem itself and production of a variety of solutions are called for, not selection among a set of fixed alternatives.”
  • On students and the scores they are to contribute to the teacher evaluation formula: “Students varying in their readiness to profit from instruction are said to differ in aptitude. Not only general cognitive abilities, but relevant prior instruction, motivation, and specific inter- actions of these and other learner characteristics with features of the curriculum and instruction will affect academic growth.” In other words, one cannot simply assume all students will learn or grow at the same rate with the same teacher. Rather, they will learn at different rates given their aptitudes, their “readiness to profit from instruction,” the teachers’ instruction, and sometimes despite the teachers’ instruction or what the teacher teaches.
  • And on the formative nature of such tests, as it was then: “Teachers rarely consult standardized test results except, perhaps, for initial grouping or placement of students, and they believe that the tests are of more value to school or district administrators than to themselves.”

Sound familiar?

Reference: Haertel, E. (1986). The valid use of student performance measures for teacher evaluation. Educational Evaluation and Policy Analysis, 8(1), 45-60.

Another Oldie but Still Very Relevant Goodie, by McCaffrey et al.

I recently re-read an article in full that is now 10 years old, or 10 years out, as published in 2004 and, as per the words of the authors, before VAM approaches were “widely adopted in formal state or district accountability systems.” Unfortunately, I consistently find it interesting, particularly in terms of the research on VAMs, to re-explore/re-discover what we actually knew 10 years ago about VAMs, as most of the time, this serves as a reminder of how things, most of the time, have not changed.

The article, “Models for Value-Added Modeling of Teacher Effects,” is authored by Daniel McCaffrey (Educational Testing Service [ETS] Scientist, and still a “big name” in VAM research), J. R. Lockwood (RAND Corporation Scientists),  Daniel Koretz (Professor at Harvard), Thomas Louis (Professor at Johns Hopkins), and Laura Hamilton (RAND Corporation Scientist).

At the point at which the authors wrote this article, besides the aforementioned data and data base issues, were issues with “multiple measures on the same student and multiple teachers instructing each student” as “[c]lass groupings of students change annually, and students are taught by a different teacher each year.” Authors, more specifically, questioned “whether VAM really does remove the effects of factors such as prior performance and [students’] socio-economic status, and thereby provide[s] a more accurate indicator of teacher effectiveness.”

The assertions they advanced, accordingly and as relevant to these questions, follow:

  • Across different types of VAMs, given different types of approaches to control for some of the above (e.g., bias), teachers’ contribution to total variability in test scores (as per value-added gains) ranged from 3% to 20%. That is, teachers can realistically only be held accountable for 3% to 20% of the variance in test scores using VAMs, while the other 80% to 97% of the variance (stil) comes from influences outside of the teacher’s control. A similar statistic (i.e., 1% to 14%) was similarly and recently highlighted in the recent position statement on VAMs released by the American Statistical Association.
  • Most VAMs focus exclusively on scores from standardized assessments, although I will take this one-step further now, noting that all VAMs now focus exclusively on large-scale standardized tests. This I evidenced in a recent paper I published here: Putting growth and value-added models on the map: A national overview).
  • VAMs introduce bias when missing test scores are not missing completely at random. The missing at random assumption, however, runs across most VAMs because without it, data missingness would be pragmatically insolvable, especially “given the large proportion of missing data in many achievement databases and known differences between students with complete and incomplete test data.” The really only solution here is to use “implicit imputation of values for unobserved gains using the observed scores” which is “followed by estimation of teacher effect[s] using the means of both the imputed and observe gains [together].”
  • Bias “[still] is one of the most difficult issues arising from the use of VAMs to estimate school or teacher effects…[and]…the inclusion of student level covariates is not necessarily the solution to [this] bias.” In other words, “Controlling for student-level covariates alone is not sufficient to remove the effects of [students’] background [or demographic] characteristics.” There is a reason why bias is still such a highly contested issue when it comes to VAMs (see a recent post about this here).
  • All (or now most) commonly-used VAMs assume that teachers’ (and prior teachers’) effects persist undiminished over time. This assumption “is not empirically or theoretically justified,” either, yet it persists.

These authors’ overall conclusion, again from 10 years ago but one that in many ways still stands? VAMs “will often be too imprecise to support some of [its] desired inferences” and uses including, for example, making low- and high-stakes decisions about teacher effects as produced via VAMs. “[O]btaining sufficiently precise estimates of teacher effects to support ranking [and such decisions] is likely to [forever] be a challenge.”

Special Issue of “Educational Researcher” (Paper #9 of 9): Amidst the “Blooming Buzzing Confusion”

Recall that the peer-reviewed journal Educational Researcher (ER) – published a “Special Issue” including nine articles examining value-added measures (VAMs). I have reviewed the last of nine articles (#9 of 9), which is actually a commentary titled “Value Added: A Case Study in the Mismatch Between Education Research and Policy.” This commentary is authored by Stephen Raudenbush – Professor of Sociology and Public Policy Studies at the University of Chicago.

Like with the last two commentaries reviewed here and here, Raudenbush writes of the “Special Issue” that, in this topical area, “[r]esearchers want their work to be used, so we flirt with the idea that value-added research tells us how to improve schooling…[Luckily, perhaps] this volume has some potential to subdue this flirtation” (p. 138).

Raudenbush positions the research covered in this “Special Issue,” as well as the research on teacher evaluation and education in general, as being conducted amidst the “blooming buzzing confusion” (p. 138) surrounding the messy world through which we negotiate life. This is why “specific studies don’t tell us what to do, even if they sometimes have large potential for informing expert judgment” (p. 138).

With that being said, “[t]he hard question is how to integrate the new research on teachers with other important strands of research [e.g., effective schools research] in order to inform rather than distort practical judgment” (p. 138). Echoing Susan Moore Johnson’s sentiments, reviewed as article #6 here, this is appropriately hard if we are to augment versus undermine “our capacity to mobilize the “social capital” of the school to strengthen the human capital of the teacher” (p. 138).

On this note, and “[i]n sum, recent research on value added tells us that, by using data from student perceptions, classroom observations, and test score growth, we can obtain credible evidence [albeit weakly related evidence, referring to the Bill & Melinda Gates Foundation’s MET studies] of the relative effectiveness of a set of teachers who teach similar kids [emphasis added] under similar conditions [emphasis added]…[Although] if a district administrator uses data like that collected in MET, we can anticipate that an attempt to classify teachers for personnel decisions will be characterized by intolerably high error rates [emphasis added]. And because districts can collect very limited information, a reliance on district-level data collection systems will [also] likely generate…distorted behavior[s]..in which teachers attempt to “game” the
comparatively simple indicators,” or system (p. 138-139).

Accordingly, “[a]n effective school will likely be characterized by effective ‘distributed’ leadership, meaning that expert teachers share responsibility for classroom observation, feedback, and frequent formative assessments of student learning. Intensive professional development combined with classroom follow-up generates evidence about teacher learning and teacher improvement. Such local data collection efforts [also] have some potential to gain credibility among teachers, a virtue that seems too often absent” (p. 140).

This, might be at least a significant part of the solution.

“If the school is potentially rich in information about teacher effectiveness and teacher improvement, it seems to follow that key personnel decisions should be located firmly at the school level..This sense of collective efficacy [accordingly] seems to be a key feature of…highly effective schools” (p. 140).

*****

If interested, see the Review of Article #1 – the introduction to the special issue here; see the Review of Article #2 – on VAMs’ measurement errors, issues with retroactive revisions, and (more) problems with using standardized tests in VAMs here; see the Review of Article #3 – on VAMs’ potentials here; see the Review of Article #4 – on observational systems’ potentials here; see the Review of Article #5 – on teachers’ perceptions of observations and student growth here; see the Review of Article (Essay) #6 – on VAMs as tools for “egg-crate” schools here; see the Review of Article (Commentary) #7 – on VAMs situated in their appropriate ecologies here; and see the Review of Article #8, Part I – on a more research-based assessment of VAMs’ potentials here and Part II on “a modest solution” provided to us by Linda Darling-Hammond here.

Article #9 Reference: Raudenbush, S. W. (2015). Value added: A case study in the mismatch between education research and policy. Educational Researcher, 44(2), 138-141. doi:10.3102/0013189X15575345

 

 

 

Special Issue of “Educational Researcher” (Paper #8 of 9, Part I): A More Research-Based Assessment of VAMs’ Potentials

Recall that the peer-reviewed journal Educational Researcher (ER) – published a “Special Issue” including nine articles examining value-added measures (VAMs). I have reviewed the next of nine articles (#8 of 9), which is actually a commentary titled “Can Value-Added Add Value to Teacher Evaluation?” This commentary is authored by Linda Darling-Hammond – Professor of Education, Emeritus, at Stanford University.

Like with the last commentary reviewed here, Darling-Hammond reviews some of the key points taken from the five feature articles in the aforementioned “Special Issue.” More specifically, though, Darling-Hammond “reflect[s] on [these five] articles’ findings in light of other work in this field, and [she] offer[s her own] thoughts about whether and how VAMs may add value to teacher evaluation” (p. 132).

She starts her commentary with VAMs “in theory,” in that VAMs COULD accurately identify teachers’ contributions to student learning and achievement IF (and this is a big IF) the following three conditions were met: (1) “student learning is well-measured by tests that reflect valuable learning and the actual achievement of individual students along a vertical scale representing the full range of possible achievement measures in equal interval units” (2) “students are randomly assigned to teachers within and across schools—or, conceptualized another way, the learning conditions and traits of the group of students assigned to one teacher do not vary substantially from those assigned to another;” and (3) “individual teachers are the only contributors to students’ learning over the period of time used for measuring gains” (p. 132).

None of things are actual true (or near to true, nor will they likely ever be true) in educational practice, however. Hence, the errors we continue to observe that continue to prevent VAM use for their intended utilities, even with the sophisticated statistics meant to mitigate errors and account for the above-mentioned, let’s call them, “less than ideal” conditions.

Other pervasive and perpetual issues surrounding VAMs as highlighted by Darling-Hammond, per each of the three categories above, pertain to (1) the tests used to measure value-added is that the tests are very narrow, focus on lower level skills, and are manipulable. These tests in their current form cannot effectively measure the learning gains of a large share of students who are above or below grade level given a lack of sufficient coverage and stretch. As per Haertel (2013, as cited in Darling-Hammond’s commentary), this “translates into bias against those teachers working with the lowest-performing or the highest-performing classes’…and “those who teach in tracked school settings.” It is also important to note here that the new tests created by the Partnership for Assessing Readiness for College and Careers (PARCC) and Smarter Balanced, multistate consortia “will not remedy this problem…Even though they will report students’ scores on a vertical scale, they will not be able to measure accurately the achievement or learning of students who started out below or above grade level” (p.133).

With respect to (2) above, on the equivalence (or rather non-equivalence) of groups of student across teachers classrooms who are the ones whose VAM scores are relativistically compared, the main issue here is that “the U.S. education system is the one of most segregated and unequal in the industrialized world…[likewise]…[t]he country’s extraordinarily high rates of childhood poverty, homelessness, and food insecurity are not randomly distributed across communities…[Add] the extensive practice of tracking to the mix, and it is clear that the assumption of equivalence among classrooms is far from reality” (p. 133). Whether sophisticated statistics can control for all of this variation is one of most debated issues surrounding VAMs and their levels of outcome bias, accordingly.

And as per (3) above, “we know from decades of educational research that many things matter for student achievement aside from the individual teacher a student has at a moment in time for a given subject area. A partial list includes the following [that are also supposed to be statistically controlled for in most VAMs, but are also clearly not controlled for effectively enough, if even possible]: (a) school factors such as class sizes, curriculum choices, instructional time, availability of specialists, tutors, books, computers, science labs, and other resources; (b) prior teachers and schooling, as well as other current teachers—and the opportunities for professional learning and collaborative planning among them; (c) peer culture and achievement; (d) differential summer learning gains and losses; (e) home factors, such as parents’ ability to help with homework, food and housing security, and physical and mental support or abuse; and (e) individual student needs, health, and attendance” (p. 133).

“Given all of these influences on [student] learning [and achievement], it is not surprising that variation among teachers accounts for only a tiny share of variation in achievement, typically estimated at under 10%” (see, for example, highlights from the American Statistical Association’s (ASA’s) Position Statement on VAMs here). “Suffice it to say [these issues]…pose considerable challenges to deriving accurate estimates of teacher effects…[A]s the ASA suggests, these challenges may have unintended negative effects on overall educational quality” (p. 133). “Most worrisome [for example] are [the] studies suggesting that teachers’ ratings are heavily influenced [i.e., biased] by the students they teach even after statistical models have tried to control for these influences” (p. 135).

Other “considerable challenges” include: VAM output are grossly unstable given the swings and variations observed in teacher classifications across time, and VAM output are “notoriously imprecise” (p. 133) given the other errors observed as caused, for example, by varying class sizes (e.g., Sean Corcoran (2010) documented with New York City data that the “true” effectiveness of a teacher ranked in the 43rd percentile could have had a range of possible scores from the 15th to the 71st percentile, qualifying as “below average,” “average,” or close to “above average). In addition, practitioners including administrators and teachers are skeptical of these systems, and their (appropriate) skepticisms are impacting the extent to which they use and value their value-added data, noting that they value their observational data (and the professional discussions surrounding them) much more. Also important is that another likely unintended effect exists (i.e., citing Susan Moore Johnson’s essay here) when statisticians’ efforts to parse out learning to calculate individual teachers’ value-added causes “teachers to hunker down and focus only on their own students, rather than working collegially to address student needs and solve collective problems” (p. 134). Related, “the technology of VAM ranks teachers against each other relative to the gains they appear to produce for students, [hence] one teacher’s gain is another’s loss, thus creating disincentives for collaborative work” (p. 135). This is what Susan Moore Johnson termed the egg-crate model, or rather the egg-crate effects.

Darling-Hammond’s conclusions are that VAMs have “been prematurely thrust into policy contexts that have made it more the subject of advocacy than of careful analysis that shapes its use. There is [good] reason to be skeptical that the current prescriptions for using VAMs can ever succeed in measuring teaching contributions well (p. 135).

Darling-Hammond also “adds value” in one whole section (highlighted in another post forthcoming here), offering a very sound set of solutions, using VAMs for teacher evaluations or not. Given it’s rare in this area of research we can focus on actual solutions, this section is a must read. If you don’t want to wait for the next post, read Darling-Hammond’s “Modest Proposal” (p. 135-136) within her larger article here.

In the end, Darling-Hammond writes that, “Trying to fix VAMs is rather like pushing on a balloon: The effort to correct one problem often creates another one that pops out somewhere else” (p. 135).

*****

If interested, see the Review of Article #1 – the introduction to the special issue here; see the Review of Article #2 – on VAMs’ measurement errors, issues with retroactive revisions, and (more) problems with using standardized tests in VAMs here; see the Review of Article #3 – on VAMs’ potentials here; see the Review of Article #4 – on observational systems’ potentials here; see the Review of Article #5 – on teachers’ perceptions of observations and student growth here; see the Review of Article (Essay) #6 – on VAMs as tools for “egg-crate” schools here; and see the Review of Article (Commentary) #7 – on VAMs situated in their appropriate ecologies here.

Article #8, Part I Reference: Darling-Hammond, L. (2015). Can value-added add value to teacher evaluation? Educational Researcher, 44(2), 132-137. doi:10.3102/0013189X15575346

Everything is Bigger (and Badder) in Texas: Houston’s Teacher Value-Added System

Last November, I published a post about “Houston’s “Split” Decision to Give Superintendent Grier $98,600 in Bonuses, Pre-Resignation.” Thereafter, I engaged some of my former doctoral students to further explore some data from Houston Independent School District (HISD), and what we collectively found and wrote up was just published in the highly-esteemed Teachers College Record journal (Amrein-Beardsley, Collins, Holloway-Libell, & Paufler, 2016). To view the full commentary, please click here.

In this commentary we discuss HISD’s highest-stakes use of its Education Value-Added Assessment System (EVAAS) data – the value-added system HISD pays for at an approximate rate of $500,000 per year. This district has used its EVAAS data for more consequential purposes (e.g., teacher merit pay and termination) than any other state or district in the nation; hence, HISD is well known for its “big use” of “big data” to reform and inform improved student learning and achievement throughout the district.

We note in this commentary, however, that as per the evidence, and more specifically the recent release of the Texas’s large-scale standardized test scores, that perhaps attaching such high-stakes consequences to teachers’ EVAAS output in Houston is not working as district leaders have, now for years, intended. See, for example, the recent test-based evidence comparing the state of Texas v. HISD, illustrated below.

Figure 1

“Perhaps the district’s EVAAS system is not as much of an “educational-improvement and performance-management model that engages all employees in creating a culture of excellence” as the district suggests (HISD, n.d.a). Perhaps, as well, we should “ponder the specific model used by HISD—the aforementioned EVAAS—and [EVAAS modelers’] perpetual claims that this model helps teachers become more “proactive [while] making sound instructional choices;” helps teachers use “resources more strategically to ensure that every student has the chance to succeed;” or “provides valuable diagnostic information about [teachers’ instructional] practices” so as to ultimately improve student learning and achievement (SAS Institute Inc., n.d.).

The bottom line, though, is that “Even the simplest evidence presented above should at the very least make us question this particular value-added system, as paid for, supported, and applied in Houston for some of the biggest and baddest teacher-level consequences in town.” See, again, the full text and another, similar graph in the commentary, linked  here.

*****

References:

Amrein-Beardsley, A., Collins, C., Holloway-Libell, J., & Paufler, N. A. (2016). Everything is bigger (and badder) in Texas: Houston’s teacher value-added system. [Commentary]. Teachers College Record. Retrieved from http://www.tcrecord.org/Content.asp?ContentId=18983

Houston Independent School District (HISD). (n.d.a). ASPIRE: Accelerating Student Progress Increasing Results & Expectations: Welcome to the ASPIRE Portal. Retrieved from http://portal.battelleforkids.org/Aspire/home.html

SAS Institute Inc. (n.d.). SAS® EVAAS® for K–12: Assess and predict student performance with precision and reliability. Retrieved from www.sas.com/govedu/edu/k12/evaas/index.html

A Retired Massachusetts Principal on her Teachers’ “Value-Added”

A retired Massachusetts principal, named Linda Murdock, posted a post on her blog titled “Murdock’s EduCorner” about her experiences, as a principal, with “value-added,” or more specifically in her state the use of Student Growth Percentile (SGP) scores to estimate said “value-added.” It’s certainly worth reading as one thing I continue to find is that which we continue to find in the research on value-added models (VAMs) is also being realized by practitioners in the schools being required to use value-added output such as these. In this case, for example, while Murdock does not discuss the technical terms we use in the research (e.g., reliability, validity, and bias), she discusses these in pragmatic, real terms (e.g., year-to-year fluctuations, lack of relationship of SGP scores and other indicators of teacher effectiveness, and the extent to which certain sets of students can hinder teachers’ demonstrated growth or value-added, respectively). Hence, do give her post a read here, and also pasted in full below. Do also pay special attention to the bulleted sections in which she discusses these and other issues on a case-by-case basis.

Murdock writes:

At the end of the last school year, I was chatting with two excellent teachers, and our conversation turned to the new state-mandated teacher evaluation system and its use of student “growth scores” (“Student Growth Percentiles” or “SGPs” in Massachusetts) to measure a teacher’s “impact on student learning.”

“Guess we didn’t have much of an impact this year,” said one teacher.

The other teacher added, “It makes you feel about this high,” showing a tiny space between her thumb and forefinger.

Throughout the school, comments were similar — indicating that a major “impact” of the new evaluation system is demoralizing and discouraging teachers. (How do I know, by the way, that these two teachers are excellent? I know because I worked with them as their principal – being in their classrooms, observing and offering feedback, talking to parents and students, and reviewing products demonstrating their students’ learning – all valuable ways of assessing a teacher’s “impact”.)

According to the Massachusetts Department of Elementary and Secondary Education (“DESE”), the new evaluation system’s goals include promoting the “growth and development of leaders and teachers,” and recognizing “excellence in teaching and leading.” The DESE website indicates that the DESE considers a teacher’s median SGP as an appropriate measure of that teacher’s “impact on student learning”:

“ESE has confidence that SGPs are a high quality measure of student growth. While the precision of a median SGP decreases with fewer students, median SGP based on 8-19 students still provides quality information that can be included in making a determination of an educator’s impact on students.”

Given the many concerns about the use of “value-added measurement” tools (such as SGPs) in teacher evaluation, this confidence is difficult to understand, particularly as applied to real teachers in real schools. Considerable research notes the imprecision and variability of these measures as applied to the evaluation of individual teachers. On the other side, experts argue that use of an “imperfect measure” is better than past evaluation methods. Theories aside, I believe that the actual impact of this “measure” on real people in real schools is important.

As a principal, when I first heard of SGPs I was curious. I wondered whether the data would actually filter out other factors affecting student performance, such as learning disabilities, English language proficiency, or behavioral challenges, and I wondered if the data would give me additional information useful in evaluating teachers.

Unfortunately, I found that SGPs did not provide useful information about student growth or learning, and median SGPs were inconsistent and not correlated with teaching skill, at least for the teachers with whom I was working. In two consecutive years of SGP data from our Massachusetts elementary school:

  • One 4th grade teacher had median SGPs of 37 (ELA) and 36 (math) in one year, and 61.5 and 79 the next year. The first year’s class included students with disabilities and the next year’s did not.
  • Two 4th grade teachers who co-teach their combined classes (teaching together, all students, all subjects) had widely differing median SGPs: one teacher had SGPs of 44 (ELA) and 42 (math) in the first year and 40 and 62.5 in the second, while the other teacher had SGPs of 61 and 50 in the first year and 41 and 45 in the second.
  • A 5th grade teacher had median SGPs of 72.5 and 64 for two math classes in the first year, and 48.5, 26, and 57 for three math classes in the following year. The second year’s classes included students with disabilities and English language learners, but the first year’s did not.
  • Another 5th grade teacher had median SGPs of 45 and 43 for two ELA classes in the first year, and 72 and 64 in the second year. The first year’s classes included students with disabilities and students with behavioral challenges while the second year’s classes did not.

As an experienced observer/evaluator, I found that median SGPs did not correlate with teachers’ teaching skills but varied with class composition. Stronger teachers had the same range of SGPs in their classes as teachers with weaker skills, and median SGPs for a new teacher with a less challenging class were higher than median SGPs for a highly skilled veteran teacher with a class that included English language learners.

Furthermore, SGP data did not provide useful information regarding student growth. In analyzing students’ SGPs, I noticed obvious general patterns: students with disabilities had lower SGPs than students without disabilities, English language learners had lower SGPs than students fluent in English, students who had some kind of trauma that year (e.g., parents’ divorce) had lower SGPs, and students with behavioral/social issues had lower SGPs. SGPs were correlated strongly with test performance: in one year, for example, the median ELA SGP for students in the “Advanced” category was 88, compared with 51.5 for “Proficient” students, 19.5 for “Needs Improvement,” and 5 for the “Warning” category.

There were also wide swings in student SGPs, not explainable except perhaps by differences in student performance on particular test days. One student with disabilities had an SGP of 1 in the first year and 71 in the next, while another student had SGPs of 4 in ELA and 94 in math in 4th grade and SGPs of 50 in ELA and 4 in math in 5th grade, both with consistent district test scores.

So how does this “information” impact real people in a real school?  As a principal, I found that it added nothing to what I already knew about the teaching and learning in my school. Using these numbers for teacher evaluation does, however, negatively impact schools: it demoralizes and discourages teachers, and it has the potential to affect class and teacher assignments.

In real schools, student and teacher assignments are not random. Students are grouped for specific purposes, and teachers are assigned classes for particular reasons. Students with disabilities and English language learners are often grouped to allow specialists, such as the speech/language teacher or the ELL teacher, to work more effectively with them. Students with behavioral issues are sometimes placed in special classes, and are often assigned to teachers who work particularly well with them. Leveled classes (AP, honors, remedial), create different student combinations, and teachers are assigned particular classes based on the administrator’s judgment of which teachers will do the best with which classes. For example, I would assign new or struggling teachers less challenging classes so I could work successfully with them on improving their skills.

In the past, when I told a teacher that he/she had a particularly challenging class, because he/she could best work with these students, he/she generally cheerfully accepted the challenge, and felt complimented on his/her skills. Now, that teacher could be concerned about the effect of that class on his/her evaluation. Teachers may be reluctant to teach lower level courses, or to work with English language learners or students with behavioral issues, and administrators may hesitate to assign the most challenging classes to the most skilled teachers.

In short, in my experience, the use of this type of “value-added” measurement provides no useful information and has a negative impact on real teachers and real administrators in real schools. If “data” is not only not useful, but actively harmful, to those who are supposedly benefitting from using it, what is the point? Why is this continuing?

In Schools, Teacher Quality Matters Most

Education Next — a non peer-reviewed journal with a mission to “steer a steady course, presenting the facts as best they can be determined…[while]…partak[ing] of no program, campaign, or ideology,” although these last claims are certainly of controversy (see, for example, here and here) — just published an article titled “In Schools, Teacher Quality Matters Most” as part of the journal’s series commemorating the 50th anniversary of James Coleman’s (and colleagues’) groundbreaking 1966 report, “Equality of Educational Opportunity.”

For background, the purpose of The Coleman Report was to assess the equal educational opportunities provided to children of different race, color, religion, and national origin. The main finding was that what we know today as students of color (although African American students were of primary focus in this study), who are (still) often denied equal educational opportunities due to a variety of factors, are largely and unequally segregated across America’s public schools, especially as segregated from their white and wealthier peers. These disparities were most notable via achievement measures, and what we know today as “the achievement gap.” Accordingly, Coleman et al. argued that equal opportunities for students in said schools mattered (and continue to matter) much more for these traditionally marginalized and segregated students than for those who were/are whiter and more economically fortunate. In addition, Coleman argued that out-of-school influences also mattered much more than in-school influences on said achievement. On this point, though, The Coleman Report was of great controversy, and (mis)interpreted as (still) supporting arguments that students’ teachers and schools do/don’t matter as much as students’ families and backgrounds do.

Hence, the Education Next article of focus in this post takes this up, 50 years later, and post the advent of value-added models (VAMs) as better measures than those to which Coleman and his colleagues had access. The article is authored by Dan Goldhaber — a Professor at the University of Washington Bothell, Director of the National Center for Analysis of Longitudinal Data in Education Research (CALDER), and a Vice-President at the American Institutes of Research (AIR). AIR is one of our largest VAM consulting/contract firms, and Goldabher is, accordingly, perhaps one of the field’s most vocal proponents of VAMs and their capacities to both measure and increase teachers’ noteworthy effects (see, for example here); hence, it makes sense he writes about said teacher effects in this article, and in this particular journal (see, for example, Education Next’s Editorial and Editorial Advisory Board members here).

Here is his key claim.

Goldhaber argues that The Coleman Report’s “conclusions about the importance of teacher quality, in particular, have stood the test of time, which is noteworthy, [especially] given that today’s studies of the impacts of teachers [now] use more-sophisticated statistical methods and employ far better data” (i.e., VAMs). Accordingly, Goldhaber’s primary conclusion is that “the main way that schools affect student outcomes is through the quality of their teachers.”

Note that Goldhaber does not offer in this article much evidence, other than evidence not cited or provided by some of his econometric friends (e.g., Raj Chetty). Likewise, Goldhaber cites none of the literature coming from educational statistics, even though recent estimates [1] suggest that approximately 83% of articles written since 1893 (the year in which the first article about VAMs was ever published, in the Journal of Political Economy) on this topic have been published in educational journals, and 14% have been published in economics journals (3% have been published in education finance journals). Hence, what we are clearly observing as per the literature on this topic are severe slants in perspective, especially when articles such as these are written by econometricians, versus educational researchers and statisticians, who often marginalize the research of their education, discipline-based colleagues.

Likewise, Goldhaber does not cite or situate any of his claims within the recent report released by the American Statistical Association (ASA), in which it is written that “teachers account for about 1% to 14% of the variability in test scores.” While teacher effects do matter, they do not matter nearly as much as many, including many/most VAM proponents including Goldhaber, would like us to naively accept and believe. The truth of the matter is is that teachers do indeed matter, in many ways including their impacts on students’ affects, motivations, desires, aspirations, senses of efficacy, and the like, all of which are not estimated on the large-scale standardized tests that continue to matter and that are always the key dependent variables across these and all VAM-based studies today. As Coleman argued 50 years ago, as recently verified by the ASA, students’ out-of-school and out-of-classroom environments matter more, as per these dependent variables or measures.

I think I’ll take ASA’s “word” on this, also as per Coleman’s research 50 years prior.

*****

[1] Reference removed as the manuscript is currently under blind peer-review. Email me if you have any questions at audrey.beardsley@asu.edu

Special Issue of “Educational Researcher” (Paper #7 of 9): VAMs Situated in Appropriate Ecologies

Recall that the peer-reviewed journal Educational Researcher (ER) – recently published a “Special Issue” including nine articles examining value-added measures (VAMs). I have reviewed the next of nine articles (#7 of 9), which is actually a commentary titled “The Value in Value-Added Depends on the Ecology.” This commentary is authored by Henry Braun – Professor of Education and Public Policy, Educational Research, Measurement, and Evaluation at Boston College (also the author of a previous post on this site here).

In this article Braun, importantly, makes explicit the assumptions on which this special issue of ER is based; that is, on assumptions that (1) too many students in America’s public schools are being inadequately educated, (2) evaluation systems as they currently exist “require radical overhaul,” and (3) it is therefore essential to use student test performance with low- and high-stakes attached to improve that which educators do (or don’t do) to adequately address the first assumption. There are counterarguments Braun also offers to readers on each of these assumptions (see p. 127), but more importantly he makes evident that the focus of this special issue is situated otherwise, as in line with current education policies. This special issue, overall, then “raise[s] important questions regarding the potential for high-stakes, test-driven educator accountability systems to contribute to raising student achievement” (p. 127).

Given this context, the “value-added” provided within this special issue, again according to Braun, is that the authors of each of the five main research articles included report on how VAM output actually plays out in practice, given “careful consideration to how the design and implementation of teacher evaluation systems could be modified to enhance the [purportedly, see comments above] positive impact of accountability and mitigate the negative consequences” at the same time (p. 127). In other words, if we more or less agree to the aforementioned assumptions, also given the educational policy context influence, perpetuating, or actually forcing these assumptions, these articles should help others better understand VAMs’ and observational systems’ potentials and perils in practice.

At the same time, Braun encourages us to note that “[t]he general consensus is that a set of VAM scores does contain some useful information that meaningfully differentiates among teachers, especially in the tails of the distribution [although I would argue bias has a role here]. However, individual VAM scores do suffer from high variance and low year-to-year stability as well as an undetermined amount of bias [which may be greater in the tails of the distribution]. Consequently, if VAM scores are to be used for evaluation, they should not be given inordinate weight and certainly not treated as the “gold standard” to which all other indicators must be compared” (p. 128).

Likewise, it’s important to note that IF consequences are to be attached to said indicators of teacher evaluation (i.e., VAM and observational data), there should be validity evidence made available and transparent to warrant the inferences and decisions to be made, and the validity evidence “should strongly support a causal [emphasis added] argument” (p. 128). However, both indicators still face major “difficulties in establishing defensible causal linkage[s]” as theorized, and desired (p. 128); hence, this prevents validity in inference. What does not help, either, is when VAM scores are given precedence over other indicators OR when principals align teachers’ observational scores with the same teachers’ VAM scores given the precedence often given to (what are often viewed as the superior, more objective) VAM-based measures. This sometimes occurs given external pressures (e.g., applied by superintendents) to artificially conflate, in this case, levels of agreement between indicators (i.e., convergent validity).

Related, in the section Braun titles his “Trio of Tensions,” (p. 129) he notes that (1) [B]oth accountability and improvement are undermined, as attested to by a number of the articles in this issue. In the current political and economic climate, [if possible] it will take thoughtful and inspiring leadership at the state and district levels to create contexts in which an educator evaluation system constructively fulfills its roles with respect to both public accountability and school improvement” (p. 129-130); (2) [T]he chasm between the technical sophistication of the various VAM[s] and the ability of educators to appreciate what these models are attempting to accomplish…sow[s] further confusion…[hence]…there must be ongoing efforts to convey to various audiences the essential issues—even in the face of principled disagreements among experts on the appropriate roles(s) for VAM[s] in educator evaluations” (p. 130); and finally (3) [H]ow to balance the rights of students to an adequate education and the rights of teachers to fair evaluations and due process [especially for]…teachers who have value-added scores and those who teach in subject-grade combinations for which value-added scores are not feasible…[must be addressed; this] comparability issue…has not been addressed but [it] will likely [continue to] rear its [ugly] head” (p. 130).

In the end, Braun argues for another “Trio,” but this one including three final lessons: (1) “although the concerns regarding the technical properties of VAM scores are not misplaced, they are not necessarily central to their reputation among teachers and principals. [What is central is]…their links to tests of dubious quality, their opaqueness in an atmosphere marked by (mutual) distrust, and the apparent lack of actionable information that are largely responsible for their poor reception” (p. 130); (2) there is a “very substantial, multiyear effort required for proper implementation of a new evaluation system…[related, observational] ratings are not a panacea. They, too, suffer from technical deficiencies and are the object of concern among some teachers because of worries about bias” (p. 130); and (3) “legislators and policymakers should move toward a more ecological approach [emphasis added; see also the Review of Article (Essay) #6 – on VAMs as tools for “egg-crate” schools here] to the design of accountability systems; that is, “one that takes into account the educational and political context for evaluation, the behavioral responses and other dynamics that are set in motion when a new regime of high-stakes accountability is instituted, and the long-term consequences of operating the system” (p. 130).

*****

If interested, see the Review of Article #1 – the introduction to the special issue here; see the Review of Article #2 – on VAMs’ measurement errors, issues with retroactive revisions, and (more) problems with using standardized tests in VAMs here; see the Review of Article #3 – on VAMs’ potentials here; see the Review of Article #4 – on observational systems’ potentials here; see the Review of Article #5 – on teachers’ perceptions of observations and student growth here; and see the Review of Article (Essay) #6 – on VAMs as tools for “egg-crate” schools here.

Article #7 Reference: Braun, H. (2015). The value in value-added depends on the ecology. Educational Researcher, 44(2), 127-131. doi:10.3102/0013189X15576341

Houston Lawsuit Update, with Summary of Expert Witnesses’ Findings about the EVAAS

Recall from a prior post that a set of teachers in the Houston Independent School District (HISD), with the support of the Houston Federation of Teachers (HFT) are taking their district to federal court to fight for their rights as professionals, and how their value-added scores, derived via the Education Value-Added Assessment System (EVAAS), have allegedly violated them. The case, Houston Federation of Teachers, et al. v. Houston ISD, is to officially begin in court early this summer.

More specifically, the teachers are arguing that EVAAS output are inaccurate, the EVAAS is unfair, that teachers are being evaluated via the EVAAS using tests that do not match the curriculum they are to teach, that the EVAAS system fails to control for student-level factors that impact how well teachers perform but that are outside of teachers’ control (e.g., parental effects), that the EVAAS is incomprehensible and hence very difficult if not impossible to actually use to improve upon their instruction (i.e., actionable), and, accordingly, that teachers’ due process rights are being violated because teachers do not have adequate opportunities to change as a results of their EVAAS results.

The EVAAS is the one value-added model (VAM) on which I’ve conducted most of my research, also in this district (see, for example, here, here, here, and here); hence, I along with Jesse Rothstein – Professor of Public Policy and Economics at the University of California – Berkeley, who also conducts extensive research on VAMs – are serving as the expert witnesses in this case.

What was recently released regarding this case is a summary of the contents of our affidavits, as interpreted by authors of the attached “EVAAS Litigation UPdate,” in which the authors declare, with our and others’ research in support, that “Studies Declare EVAAS ‘Flawed, Invalid and Unreliable.” Here are the twelve key highlights, again, as summarized by the authors of this report and re-summarized, by me, below:

  1. Large-scale standardized tests have never been validated for their current uses. In other words, as per my affidavit, “VAM-based information is based upon large-scale achievement tests that have been developed to assess levels of student achievement, but not levels of growth in student achievement over time, and not levels of growth in student achievement over time that can be attributed back to students’ teachers, to capture the teachers’ [purportedly] causal effects on growth in student achievement over time.”
  2. The EVAAS produces different results from another VAM. When, for this case, Rothstein constructed and ran an alternative, albeit sophisticated VAM using data from HISD both times, he found that results “yielded quite different rankings and scores.” This should not happen if these models are indeed yielding indicators of truth, or true levels of teacher effectiveness from which valid interpretations and assertions can be made.
  3. EVAAS scores are highly volatile from one year to the next. Rothstein, when running the actual data, found that while “[a]ll VAMs are volatile…EVAAS growth indexes and effectiveness categorizations are particularly volatile due to the EVAAS model’s failure to adequately account for unaccounted-for variation in classroom achievement.” In addition, volatility is “particularly high in grades 3 and 4, where students have relatively few[er] prior [test] scores available at the time at which the EVAAS scores are first computed.”
  4. EVAAS overstates the precision of teachers’ estimated impacts on growth. As per Rothstein, “This leads EVAAS to too often indicate that teachers are statistically distinguishable from the average…when a correct calculation would indicate that these teachers are not statistically distinguishable from the average.”
  5. Teachers of English Language Learners (ELLs) and “highly mobile” students are substantially less likely to demonstrate added value, as per the EVAAS, and likely most/all other VAMs. This, what we term as “bias,” makes it “impossible to know whether this is because ELL teachers [and teachers of highly mobile students] are, in fact, less effective than non-ELL teachers [and teachers of less mobile students] in HISD, or whether it is because the EVAAS VAM is biased against ELL [and these other] teachers.”
  6. The number of students each teacher teaches (i.e., class size) also biases teachers’ value-added scores. As per Rothstein, “teachers with few linked students—either because they teach small classes or because many of the students in their classes cannot be used for EVAAS calculations—are overwhelmingly [emphasis added] likely to be assigned to the middle effectiveness category under EVAAS (labeled “no detectable difference [from average], and average effectiveness”) than are teachers with more linked students.”
  7. Ceiling effects are certainly an issue. Rothstein found that in some grades and subjects, “teachers whose students have unusually high prior year scores are very unlikely to earn high EVAAS scores, suggesting that ‘ceiling effects‘ in the tests are certainly relevant factors.” While EVAAS and HISD have previously acknowledged such problems with ceiling effects, they apparently believe these effects are being mediated with the new and improved tests recently adopted throughout the state of Texas. Rothstein, however, found that these effects persist even given the new and improved.
  8. There are major validity issues with “artificial conflation.” This is a term I recently coined to represent what is happening in Houston, and elsewhere (e.g., Tennessee), when district leaders (e.g., superintendents) mandate or force principals and other teacher effectiveness appraisers or evaluators, for example, to align their observational ratings of teachers’ effectiveness with value-added scores, with the latter being the “objective measure” around which all else should revolve, or align; hence, the conflation of the one to match the other, even if entirely invalid. As per my affidavit, “[t]o purposefully and systematically endorse the engineering and distortion of the perceptible ‘subjective’ indicator, using the perceptibly ‘objective’ indicator as a keystone of truth and consequence, is more than arbitrary, capricious, and remiss…not to mention in violation of the educational measurement field’s Standards for Educational and Psychological Testing” (American Educational Research Association (AERA), American Psychological Association (APA), National Council on Measurement in Education (NCME), 2014).
  9. Teaching-to-the-test is of perpetual concern. Both Rothstein and I, independently, noted concerns about how “VAM ratings reward teachers who teach to the end-of-year test [more than] equally effective teachers who focus their efforts on other forms of learning that may be more important.”
  10. HISD is not adequately monitoring the EVAAS system. According to HISD, EVAAS modelers keep the details of their model secret, even from them and even though they are paying an estimated $500K per year for district teachers’ EVAAS estimates. “During litigation, HISD has admitted that it has not performed or paid any contractor to perform any type of verification, analysis, or audit of the EVAAS scores. This violates the technical standards for use of VAM that AERA specifies, which provide that if a school district like HISD is going to use VAM, it is responsible for ‘conducting the ongoing evaluation of both intended and unintended consequences’ and that ‘monitoring should be of sufficient scope and extent to provide evidence to document the technical quality of the VAM application and the validity of its use’ (AERA Statement, 2015).
  11. EVAAS lacks transparency. AERA emphasizes the importance of transparency with respect to VAM uses. For example, as per the AERA Council who wrote the aforementioned AERA Statement, “when performance levels are established for the purpose of evaluative decisions, the methods used, as well as the classification accuracy, should be documented and reported” (AERA Statement, 2015). However, and in contrast to meeting AERA’s requirements for transparency, in this district and elsewhere, as per my affidavit, the “EVAAS is still more popularly recognized as the ‘black box’ value-added system.”
  12. Related, teachers lack opportunities to verify their own scores. This part is really interesting. “As part of this litigation, and under a very strict protective order that was negotiated over many months with SAS [i.e., SAS Institute Inc. which markets and delivers its EVAAS system], Dr. Rothstein was allowed to view SAS’ computer program code on a laptop computer in the SAS lawyer’s office in San Francisco, something that certainly no HISD teacher has ever been allowed to do. Even with the access provided to Dr. Rothstein, and even with his expertise and knowledge of value-added modeling, [however] he was still not able to reproduce the EVAAS calculations so that they could be verified.”Dr. Rothstein added, “[t]he complexity and interdependency of EVAAS also presents a barrier to understanding how a teacher’s data translated into her EVAAS score. Each teacher’s EVAAS calculation depends not only on her students, but also on all other students with- in HISD (and, in some grades and years, on all other students in the state), and is computed using a complex series of programs that are the proprietary business secrets of SAS Incorporated. As part of my efforts to assess the validity of EVAAS as a measure of teacher effectiveness, I attempted to reproduce EVAAS calculations. I was unable to reproduce EVAAS, however, as the information provided by HISD about the EVAAS model was far from sufficient.”