Effects of Class Size on Test Scores: Evidence from Japanese Municipal Data

Using newly available data on academic performance garnered for a survey conducted by a local government in Japan, this study analyzes the effects of class size on test scores (specifically on the subjects of English, Japanese, and mathematics). Empirical results show that class size has a negative correlation on test scores in mathematics and English. In short, smaller class size was associated with higher test scores in mathematics and English. However, this was low-impact variable compared to other variables such as scholastic year and gender. Additionally, estimation results that investigate the relationship between class size and test scores in Japanese studies lack consistency. Moreover, the relationship between class size and test scores in mathematics has a quadratic function which is convex downward. The extreme value of this quadratic function is 36.2; math test scores decrease as class size increases up to this point, and increase beyond it.