This dissertation seeks to understand how teachers learn through interactions in newly formed workplace communities by examining how mathematics teachers engaged in equity-oriented reforms frame problems of practice. It examines how teachers' framings develop over time, and how teachers' shifting frames connect to their learning in a community of practice (Wenger, 1998). Using a case study design and ethnographic methods, this research investigates the interactions of a group of high school freshman mathematics teachers who collaborate daily on issues related to equity-oriented reforms. Primary data sources are transcripts from audio-recorded collaboration team meetings, which were contextually supplemented by fieldnotes, artifacts, and teacher interviews. The members of the collaboration team were invested in equity-oriented reforms because they experienced a freshman student failure crisis in the previous year. In response to this crisis, they implemented curricular and pedagogical reforms to better support all students' learning of freshman mathematics. The interactions that emerged from teachers' interactions participation on the collaboration team revealed their framings of the struggling student problem. Analysis showed how teachers' frames of the struggling student problem shifted from diagnoses of invariable student characteristics to frames that fostered actionable responses that were proximal to their everyday instruction. Closer inspection of teachers' negotiation of meaning around these evolving frames illustrated how these shifts served to mark and describe changes in teachers' participation in their community of practice, which is a process Wenger (1998) characterizes as learning. Taken together, this analysis showed that the collaborative team teachers' learning was manifested through their framing practices. This research provides a counternarrative to static characterizations of teacher communities by showing development of a teacher community over time. Moreover, this study contributes to the literature by its use of frame analysis tools to show and describe this development, evidenced by how teachers frame problems of practice over time, which also contributes mechanisms for drawing conclusions about whether or not teachers are seeding problems they can act on or not. In addition, by linking conceptual tools from frame analysis with sociocultural theories of learning, this study provides analytic means for documenting teachers' collective learning. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]