Effects of ability mixing in high school on adulthood earnings: Quasiexperimental evidence from South Korea

We estimate impacts of ability mixing compared to ability grouping in high school education on students' adulthood earnings. To overcome endogeneity and selection problems that plagued the previous studies, we exploit a policy experiment in South Korea in the 1970s, which changed the education regime of general high schools from grouping to mixing in major cities. We find that the mixing treatment has a positive but statistically insignificant effect on average adulthood earnings. We also find that while mixing has positive effects on low ability students' adulthood earnings, it has smaller positive or even negative effects on higher ability students.