Do Small Schools Improve Performance in Large, Urban Districts? Causal Evidence from New York City

Abstract

We evaluate the effectiveness of small high school reform in the country’s largest school district, New York City. Using a rich administrative dataset for multiple cohorts of students, we estimate a model of school outcomes using instrumental variables with multiple types of endogenous school interventions. Using student residence to instrument for endogenous school selection, we find substantial heterogeneity in school effects as newly created small schools have positive effects on education outcomes while older small schools do not. Importantly, we show that ignoring this source of treatment effect heterogeneity yields a misleading zero effect of small school attendance.