Selecting Growth Measures for Use in School Evaluation Systems

Abstract

The specifics of how growth models should be constructed and used for educational evaluation is a topic of lively policy debate in states and school districts nationwide. In this article, we take up the question of model choice—framed within a policy context—and examine three competing approaches. The first approach, reflected in the popular student growth percentiles (SGPs) framework, eschews all controls for student covariates and schooling environments. The second approach, typically associated with value-added models (VAMs), controls for student-background characteristics and under some conditions can be used to identify the causal effects of educational units (i.e., districts, schools, and teachers). The third approach, also VAM-based, fully levels the playing field so that the correlation between the growth measures and student demographics is essentially zero. We argue that the third approach is the most desirable for use in school evaluation systems. Our case rests on personnel economics, incentive-design theory, and the potential role that growth measures can play in improving instruction in K-12 schools.