Abstract
Teaching assistants (TAs) play vital roles in the mathematics education of undergraduates and may become mathematics professors. From the K-12 literature, it is clear that patterns of teaching practice, as well as beliefs about teaching and learning, form early in teachers' careers. Yet, although there is a large body of research about K-12 teachers, researchers are only beginning to consider the development of TAs. This article is an effort to foster collaboration between K-12 and undergraduate mathematics educators in framing and carrying out research on the nature of TA professional development. This article contains reviews of TA professional development, descriptions of practice- and research-oriented work, analysis of similarities and differences with K-12 mathematics education, descriptions of researchable questions, and potential agendas for future work.