The Causal Effect of School Reform: Evidence from California's Quality Education Investment Act

Beginning in the 2007-08 school year, California's Quality Education Investment Act required schools selected via lottery to institute reforms including class size reduction, increased average teacher experience, and extra professional training. The act provided additional per-pupil funding for schools to meet these requirements. Conditional on known probabilities of selection, which differed across schools, treatment is uncorrelated with potential outcomes, allowing for non-parametric identification of the causal effect by inverse probability weighting. In the first fully-funded year of the program, math scores in 4th grade increased by 0.32 SD in the population of California school-grade averages, and by the second fully-funded year 5th grade math scores improved by 0.36 SD. By the third fully-funded year of the program, math scores in 2nd grade were 0.28 SD higher in the distribution of California school-grade averages, and 0.27 SD higher in 3rd grade. Selected schools did not increase teacher experience, and had 4 to 4.4 fewer students in the first fully-funded year in 4th and 5th$ grade. In kindergarten through 3rd grade class sizes were reduced later and less dramatically, by 3 to 4 students by the third fully-funded year, due primarily to unselected schools exiting California's previous class size reduction program. The timing of class size reductions and student achievement gains suggests class size was the driving factor.