Using a representative data from Korean Education Longitudinal Study(KELS), this study attempts
to investigate the structural relationship among academic self-concept of underachievers and other
variables, along with testing the moderator effect of lesson plan for the underachievers. The major
findings can be summarized as follows. First, the academic self-concept of underachievers is
significantly influenced by the parents' supporting activities and students' studying time. This implies
that if parents support their children actively, even underachievers can have a positive academic
self-concept. Second, the lesson plan for underachievers didn't show significant moderator effect in
determining their academic self-concept. Nonetheless, we can confirm the lesson plan for
underachievers can weaken the effect of family background on parents' supporting activities, and can
also enhance the effect of parents' supporting activities on the academic self-concept. These results
suggest that the lesson plan for underachievers should focus on the affective development and the
formation of positive academic self-concept for underachievers.