Instruction time varies among schools, subjects, pupils and grades. This variation is positively associated with test scores and has been used to identify modest positive causal effects for instruction hours in certain grades. We exploit administrative data on delivered and timetabled...

This paper analyzes data from Project STAR, an experiment in which 11,600 Tennessee kindergarten students and teachers were randomly assigned to one of three types of classes beginning in the 1985-86 school year: small classes (13-17 students), regular-size classes (22-25 students), and...