We exploit two unusual policy features of academic high schools in Seoul, South Korea—random assignment of pupils to high schools within districts and conversion of some existing single-sex schools to the coeducational (coed) type over time—to identify three distinct causal parameters: the...

Early retirement incentives (ERIs) are increasingly prevalent in education as districts seek to close budget gaps by replacing expensive experienced teachers with lower-cost newer teachers. Combined with the aging of the teacher workforce, these ERIs are likely to change the composition of...