This study attempts to analyze the effect of ability grouping on students' academic
self-concept and also examine whether or not social capital can mediate the positive and/or
negative effects from the ability grouping-based education. To do so, this research employs path
analyses using the 3rd wave of Korean Education Longitudinal Study, as well as in-depth
interviews with the students in lower-level class. One major finding is that there is generally
positive effect of ability grouping for students in upper-level class while it is more likely to be
negative for those in lower-level class. In addition, the mediating effects were different,
depending on three types of social capital - students' relations with teachers, peers, and parents.
As for the students' relations with teachers, they tend to diminish the positive effect of ability
grouping on the academic self-concept for the students in upper-level class while they contribute
to reduce the negative effect of ability grouping for those in lower-level class. This finding was
also supported by in-depth interview done for those in lower-level class. However, ability
grouping negatively affects the academic self-concept for both groups by worsening the
peer-relations. Finally, the relations with parents have positive effect on academic self-concept
for those in the upper-level class, but for those in the lower-level class, they have varying
effects depending on the subject of the class. Also, considering all types of social capital at the
same time, there is no clear effect of social capital on academic self-concept in counteracting
the effect of ability grouping in either positive or negative direction.