Extraordinary Asian American educational achievement has often been credited to a common cultural influence of Confucianism that emphasizes education, family honor, discipline, and respect for authority. In this article, Min Zhou and Susan Kim argue that immigration selectivity, higher than average levels of premigration and postmigration socioeconomic status, and ethnic social structures interact to create unique patterns of adaptation and social environments conducive to educational achievement. This article seeks to unpack the ethnic effect through a comparative analysis of the ethnic system of supplementary education that has developed in two immigrant communities--Chinese and Korean--in the United States. The study suggests that the cultural attributes of a group interact substantially with structural factors, particularly tangible ethnic social structures on which community forces are sustained and social capital is formed. The authors conclude that "culture" is not static and requires structural support to constantly adapt to new situations. (Contains 15 notes.)