Cross-cultural changes were accompanied by the sovereignty transition of Hong Kong during the TIMSS data collection, which triggered migration of intellectual families between Hong Kong and other places. To enhance comparability of the urban setting, this investigation focuses on Singapore and Hong Kong for having similar Chinese majority and colonial history. As both cities were reported having high student performance in science, student self-concept is articulated to examine its reciprocal relationship with science achievement under the context of non-monotonic population transition. The perspectives of comparative education have been gained through the cross-cultural understanding of empirical findings from the trend data analysis.