Drawing on first and fourth wave data from Seoul Education Longitudinal Study(SELS),
we examined the effects of autonomous private high school expansion on the achievement
gap between students of different types of high schools, using difference in
differences(DID). Results showed that gender, previous academic achievement, parental
education, parental expectation for student’s educational attainment are closely related to
student’s likelihood of attending a special-purpose high school or an autonomous private
high school. In addition, the more a student considered the characteristics of a good
school, the more likely she/he was to attend the schools listed above. Next, we compared
the pre-expansion cohort and the post-expansion cohort in order to identify those who
would attend a special-purpose high school or an autonomous private high school because
of the expansion but would not otherwise (compliers). We, then, compared changes in
compliers’ academic achievement with changes in academic achievement of two control
groups (i.e. always-takers and never-takers). We found that students from special-purpose
high schools and autonomous private high schools showed higher achievement than those
students from general high schools, which was mostly explained by differences in family
background between those students attending different types of high schools. We also
observed that the qualitative differentiation occurred among the individual special-purpose
high schools and general high schools following the expansion of autonomous private high
schools. Based on the results, we discussed briefly policy measures for bridging the
achievement gap.