Bringing the Full Picture into Focus: A Consideration of the Internal and External Validity of Charter School Effects

The authors of this chapter describe an institutional arrangement for education in the United States: the provision of education through “charter schools,” an experiment in liberalization and decentralization begun in the early 1990s. They address whether charter schools raise student achievement on average compared to students in traditional public schools. They report that the authors of small-scale randomized studies report quite positive effects, but that as the sample of schools increases, the reported effects decline in size and significance, from which they conclude that while charter schools do not generally harm student achievement, they do not have significantly positive effects for the average student. They do, however, more positively affect poor and minority students and students in some urban centers. This underlines the importance of examining school effects across different geographies and social groups and the key role external validity plays in drawing policy implications from educational research.

School Effects Revisited: The Size, Stability, and Persistence of Middle Schools’ Effects on Academic Outcomes

Since the early 2000s, educational evaluation research has primarily centered on teachers’, rather than schools’, contributions to students’ academic outcomes due to concerns that estimates of the latter were smaller, less stable, and more prone to measurement error. We argue that this disparity should be reduced. Using administrative data from three cohorts of Massachusetts public school students ( N = 123,261) and two-level models, we estimate middle schools’ value-added effects on eighth-grade and 10th-grade math scores and, importantly, a non–test score outcome: 4-year college enrollment. Comparing our results to teacher-centered studies, we find that school effects (encompassing both teaching- and nonteaching-related factors) are initially smaller but nearly as stable and perhaps more persistent than are individual teacher effects. Our study motivates future research estimating the long-term effects of both teachers and schools on a wide range of outcomes.