Studies in the U.S. have established the fact that residential and school mobility are harmful for diverse domains of child development because they bring about drastic changes in external environments. Based on this finding, we examine effects of residential and school mobility on the growth of math and Korean test scores. More specifically, we take a close look at relationship between residential and school mobility during 4th through 6th grade and academic achievement at 5th and 6th grade. For a rigorous study, we use several statistical methods including ordinary least squares, truncated regression, and a matching method. We detect negative effects of school mobility during 4th through 5th grade on math test scores at 5th grade and negative effects of school mobility during 5th through 6th grade on math test scores at 6th grade. School mobility during 4th through 5th grade appears to exert negative influence on math test scores at 6th grade though the effects are not statistically significant. We fail to find any negative impacts of residential or school mobility on Korean test scores.