To compare the ontogeny of schooling behavior between homo- and heterogeneous tadpole groups of the Japanese mountain frog (Rana ornativentris), I measured the schooling behavior of a pure group consisting only of siblings and a mixed group consisting of siblings and non-siblings weekly for 5 weeks. The mean individual and nearest-neighbor distances decreased with increasing ontogeny up to hindlimb development. However, there were no significant differences in mean distances between the pure and mixed tadpole groups. The heterogeneity prepared in this study did not affect the schooling behavior of this species.