Based on surveys and field work conducted in District C of Beijing City, the author identifies migrant children's social assimilation obstacles according to distinct school types: each school type offers different quality educational resources and is composed of migrant students at different socioeconomic levels. The survey data show that migrant children with relatively low cultural capital and social capital are more concentrated in private and self-run schools. Field work also shows migrant children in public schools encounter a major social assimilation barrier through school culture, which privileges urban culture and marginalizes rural culture; private school students experience both urban and rural hometown cultures; and self-run schools illuminate the stark contrast between policy rhetoric and the marginal status of migrant youths. In investigating the social assimilation of migrant workers and their children in Chinese cities, we should question the homogeneity of the "migrant children" group. Rather than modifying the U.S.-based social assimilation theory that is based on ethnic group differences, we should focus on the Chinese-specific, cultural, and systemic differences among migrant children subgroups. [This article was translated by Jeff Keller.]