Measuring the Impacts of Teachers I: Evaluating Bias in Teacher Value-Added Estimates

Abstract

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The effect of summer on value-added assessments of teacher and school performance

“…A comparison of the results for the null and base models shows that controlling for prior achievement reduces the summer effect considerably. Previous research has shown that controlling for prior achievement reduced selection biases in VAA estimates (Chetty, Friedman, & Rockoff, 2014;Kane & Staiger, 2008). That conclusion appears to extend to selection biases originating from the summer.…”

“…5 This model is considered the base model in that the control covariates are limited to what is typically recommended as the minimal controls for VAA. Comparing the null and base model results is instructive because recent research suggests that prior achievement is the most critical control for reducing selection biases in VAA (Chetty, Friedman, & Rockoff, 2014;Kane & Staiger, 2008). However, it is unclear whether controlling for prior achievement is also critical for addressing summer effects on VAA estimates.…”

Evaluating the Tennessee Higher Education Commission's Report Card on the value-added estimates of teacher preparation programs

“…compare experimental VAM estimates for a subset of California teachers with earlier nonexperimental estimates for the same teachers and find that they are similar, suggesting that VAMs are better than other measures of teacher quality or subjective ratings. Chetty et al (2014) find that estimated teacher effects on short-run achievement are large, and these estimates are correlated with long-run outcomes, including earnings. Other studies suggest that teachers improve in effectiveness in terms of value-added to student achievement up through at least their first four years with a leveling off after five years (Clotfelter, Ladd, & Vigdor, 2006;Rivkin, Hanushek, & Kain, 2005;Rockoff, 2004).…”

“…Simulation studies have also shown that the potential for misclassifying teachers as high-or low-performing could be substantial, particularly for teachers who teach low-performing students. More recent experimental and quasiexperimental approaches have obtained informative estimates of teacher-value added, but with some noise (Chetty et al, 2014;Staiger & Rockoff, 2010). compare experimental VAM estimates for a subset of California teachers with earlier nonexperimental estimates for the same teachers and find that they are similar, suggesting that VAMs are better than other measures of teacher quality or subjective ratings.…”

“…Researchers belonging to the first camp have compared estimates derived from different statistical methods and other technical issues involving model specification, choice of sample and outcome, and measurement error in the estimation of "teacher effects" (Chetty, Friedman, & Rockoff, 2014). Prior studies find considerable differences between the most and least effective teachers based on value-added results (Rivkin, Hanushek, & Kain, 2005;Sanders & Horn, 1998).…”