We examine how bilingual pre-service teachers developed a practice of communicating to parents their children’s mathematical thinking and how the teachers invited parents to participate in instructional practices in the mathematics classroom. We argue that these practices are knowledge-intensive, in that bilingual pre-service teachers draw on both their knowledge of children’s mathematical thinking and their own experiences as bilingual students, and that communicating this to parents reflects this knowledge. We conceptualize this knowledge as situated in, and integrated with, the practice of teaching. We therefore consider it necessary to support the development of this knowledge early in pre-service teacher education