Increasingly, teachers all over the world are grappling on a daily basis with the fact of multilingual classrooms. In this book, Jill Adler captures three inter-related dilemmas that lie at the heart of teaching mathematics in multilingual classrooms. Adler's identification and naming of the dilemma of code-switching, the dilemma of mediation, and the dilemma of transparency, arise from exploring the realities of actual classrooms, and are shaped by a perspective of teaching as a social practice. Adler provides a sharp analysis and strong theoretical grounding for her work, pulling together research related to the relationship between language and mathematics, communicating mathematics, and mathematics in bi-/multilingual settings. In so doing, she offers a direct challenge to dominant research on communication in mathematics classrooms that has `othered' the multilingual setting in its normalisation of the monolingual classroom. The `norm' is a multicultural one. Set in contemporary South Africa - a context of linguistic diversity and rapid change - this book offers a spotlight whose beam is wide enough to illuminate dilemmas at work in all mathematics classrooms.