Since at least the 1980s, motivated, in part, by findings from international comparisons of students' mathematics achievement, some American (U.S.) educators and policy makers have initiated educational reform that focuses on improving teaching practices and curriculum designs by advocating for the adoption of Asian educational models. The implicit assumption behind such reform seems to overlook the possible roles of outside of school factors in superior academic performance in the Asian countries. The purpose of this study was to investigate how outside of school factors were related to students' TIMSS mathematics achievement for the U.S and five top-performing Asian nations or regions, and to examine whether the relative role of school-associated and outside of school factors was consistent across these five Asian countries. The results indicated that students' achievement was highly related to outside of school factors across all six countries. For Singapore and Hong Kong,