In this paper, we present an analysis of the language practices of four Spanish/English dual language (DL) preschool teachers, focusing on the ways in which the teachers mediate bilingual interactions with students and distribute Spanish and English across different classroom discourse functions. Findings reveal teachers' flexible and strategic use of each language to support children's developing bilingual competencies as well as to negotiate several communicative, academic, and management functions. Findings further illuminate the utility of bilingual speech/interaction as a communicative and academic resource and suggest that a strict language separation approach, as traditionally implemented in DL programs, may be at odds with the natural social interactions of bilinguals who draw on a number of communicative strategies, including codeswitching and tandem talk, to construct meaning. (author abstract)