Value-added modeling

Abstract: We estimate the importance of teachers in Chicago public high schools using matched student‐teacher administrative data. A one standard deviation, one semester improvement in math teacher quality raises student math scores by 0.13 grade equivalents or, over 1 year, roughly one‐fifth of average yearly gains. Estimates are relatively stable over time, reasonably impervious to a variety of conditioning variables, and do not appear to be driven by classroom sorting or selective score reporting. Also, teacher quality is particularly important for lower‐ability students. Finally, traditional human capital measures—including those determining compensation—explain little of the variation in estimated quality.

Abstract: We used a random-assignment experiment in Los Angeles Unified School District to evaluate various non-experimental methods for estimating teacher effects on student test scores. Estimated teacher effects from a pre-experimental period were used to predict student achievement following random assignment of teachers to classrooms. While all of the teacher effect estimates we considered were significant predictors of student achievement under random assignment, those that controlled for prior student test scores yielded unbiased predictions and those that further controlled for mean classroom characteristics yielded the best prediction accuracy. In both the experimental and nonexperimental data, we found that teacher effects faded out by roughly 50 percent per year in the two years following teacher assignment.

Abstract: Growing concerns over the inadequate achievement of U.S. students have led to proposals to reward good teachers and penalize (or fire) bad ones . The leading method for assessing teacher quality is “value added” modeling (VAM), which decomposes students’ test scores into components attributed to student heterogeneity and to teacher quality. Implicit in the VAM approach are strong assumptions about the nature of the educational production function and the assignment of students to classrooms. In this paper, I develop falsification tests for three widely used VAM specifications , based on the idea that future teachers cannot influence students’ past achievement. In da ta from North Carolina, each of the VAMs’ exclusion restrictions are dramatically viola ted. In particular, these models indicate large “effects” of 5th grade teachers on 4th grade t est score gains. I also find that conventional measures of individual teachers’ value added fade out very quickly and are at best weakly related to long-run effects. I discuss implic ations for the use of VAMs as personnel tools.

Abstract: The extensive investigation of the contribution of teachers to student achievement produces two generally accepted results. First, there is sub stantial variation in teacher quality as measured by the value added to achievement or future aca demic attainment or earnings. Second, variables often used to determine entry into the profession and salaries, including post-graduate schooling, experience, and licensing examination scores, appear to explain little of the variation in teacher quality so measured, with the exception of early experience. Together these findings underscore explicitly that observed teacher characteristics do not represent teacher quality.