Do more school resources increase learning outcomes? Evidence from an extended school-day reform

Whether allocating more resources improves learning outcomes for students in low-performing public schools remains an open debate. We focus on the effect of increasing instructional time, which is theoretically ambiguous due to possible compensating changes in effort by students, teachers, or parents. Using a regression discontinuity design, we find that a reform extending the school day increases math test scores. It also improved reading, technical skills and socio-emotional competencies. Our results are partly explained by reductions in home production by students, specialization by teachers and investments in pedagogical assistance to teachers, in addition to the extended instructional time.