We analyze class-size effects on academic achievement in secondary school in Denmark exploiting an institutional setting where pupils cannot predict class size prior to enrollment, and where post-enrollment responses aimed at affecting realized class size are unlikely. We identify class-size effects combining a regression discontinuity design with…

This paper provides an illustration of how schools can use their extensive student databases in a way that goes beyond comparing differences between demographic subgroups. The urban district was already aware of the extent and nature of achievement gaps "between" demographic subgroups as published in accountability reports. They were in…