The study of language choice and code-switching can illuminate the ways in which, through language, social institutions with ethnolinguistically diverse staff and clients exercise symbolic domination. Using the example of French-language minority education in Ontario (Canada), this article examines the ways in which ethnic and institutional relations of power overlap or crosscut, forming constraints which have paradoxical effects. In an analysis of two classrooms, it is shown how an ideology of institutional monolingualism is supported or undermined by program structure, curriculum content, and the social organization of turn-taking, and how individuals use language choices and code-switching to collaborate with or resist these arrangements. The effect of these processes is to contain paradoxes and to produce new relations of power within the school. (Symbolic domination, choice of language, code-switching, French/English language contact, social institutions, Canada)