The study reported here concerns 4 years of collaboration between secondary school teachers and academic researchers, constituting an emerging community of inquiry into mathematics teaching. In the article, the process of forming of this community is discussed, focusing on the reflective activity developed by its members as well as the tensions and conflicts that emerged in the shaping of an inquiry identity by them. Furthermore, shifts in the mode of participation in the community and thus learning gains of all members are identified, with the teachers gradually developing an awareness of teaching practice in general, and the researchers becoming progressively acquainted with the reflexive relationship between inquiring into teaching practice and teachers' professional development.