The reciprocal relationship between mathematics achievement and self-concept is examined in this study to expand the existing knowledge to a cross-cultural setting. Based on analyses of educational data two years before and after Hong Kong's sovereignty switch in 1997, this investigation shows a weak reciprocal relationship among the eighth-grade students across gender categories. With the introduction of a new policy to promote Chinese instruction, changes in the perceived importance of English have been assessed by education stakeholders, and the results are used to indicate a latent factor of "English push" behind the learning process. In the context of cross-cultural transition, gender differences have been found in path coefficients toward mathematics achievement and self-concept. Limited by the four-year research period, one may speculate whether it would take longer to demonstrate a large effect size in the reciprocal relationship. (Contains 1 figure, 3 notes and 4 tables.)