Instructional time is a fundamental educational input, yet we have little causal evidence about the effect of longer school days on student achievement. This paper uses a sharp regression discontinuity design to estimate the effects of lengthening the school day for low-performing schools in Florida by exploiting an administrative cutoff for…

Schools frequently increase the instructional time to improve primary school children's math and reading skills. There is, however, little evidence that math and reading skills are effectively improved by these instruction-time increases. This study evaluates "Playing for Success" (PfS), an extended school day program for underachieving…