Recent mathematics education reform efforts call for the instantiation of mathematics classroom environments where students have opportunities to reason and construct their understandings as part of a community of learners. Despite some successes, traditional models of instruction still dominate the educational landscape. This limited success can be attributed, in part, to an underdeveloped understanding of the roles teachers must enact to successfully organize and participate in collaborative classroom practices. Toward this end, an in-depth longitudinal case study of a collaborative high school mathematics classroom was undertaken guided by the following two questions: What roles do these collaborative practices require of teacher and students? How does the community's capacity to engage in collaborative practices develop over time? The analyses produced two conceptual models: one of the teacher's role, along with specific instructional strategies the teacher used to organize a collaborative learning environment, and another of the process by which the class's capacity to participate in collaborative inquiry practices developed over time.