This ethnographic study investigated heritage language maintenance among two distinct groups of Chinese immigrant families (Mandarin and Fujianese) from the social network perspective. The results indicated that a co-ethnic network could be a double-edged sword, which works differently on children from different social classes. While the Mandarin children benefited from a strong co-ethnic network in resisting pressures for language assimilation, the Fujianese children shifted to English collectively as a way to survive in the U.S. society. (Contains 7 footnotes and 2 tables.)