Although not exclusive to the Republic of Korea's educafional system, the
pervasiveness of private tutoring, and its consequences, serve to distinguish it from
systems operated in other countries. This paper quantifies the impact of time spent
on private tutoring on the performance of students in the three competence fields
assessed in the Programme for International Student Assessment (PISA). Instrumental
variables are applied in a multilevel framework to address endogeneity. Our results
indicate that the impact of time dedicated to private tutoring on academic performance
depends on the parficular competence: positive. for mathematics, positive but
decreasing for reading, and non-significant for science