As school districts face increased accountability demands, administrators have turned to teacher-leaders as a key source in efforts to improve instructional practice and student learning. Unfortunately, many individuals who are selected as teacher-leaders often have little support and only limited knowledge of how they might work with peers on pedagogical and content-based instructional issues. Despite the increased attention that has been placed on teachers' roles in efforts to improve instruction, there has been little examination of how knowledgeable others (e.g., educational researchers and professional developers) might support such work. This dissertation takes up this question by studying a complementary set of tools and its role in supporting a teacher's instructional practice in her classroom, as well as with colleagues.

The first phase of this study examined what provoked a teacher to take up the tools that she encountered as part of a practice-based middle school mathematics professional development project. Next, this study analyzed how this complementary set of tools functioned to scaffold the transfer of specific instructional actions from professional development to Me teacher's practice. The final phase focused on understanding the ways in which these tools scaffolded the transfer of specific instructional actions that the teacher claimed to use with students to her work with colleagues.

The tools analyzed in this dissertation consist of one conceptually based tool and two tools of action." The conceptually based tool central to this study is the Mathematical Tasks Framework (MTF) and the primary tool of action is the Thinking Through a Lesson Protocol (TTLP) both grew out of work from the Quantitative Understanding: Amplifying Student Achievement and Reasoning (QUASAR) project. A central finding of this study is that the MTF functioned mainly to hold together a set of implicit instructional actions and ideas. The TTLP, however, scaffolded the transfer of the implicit instructional actions embedded in the MTF through its explicit and actionable prompts. Additionally, there is evidence to suggest that a secondary tool of action, the Thinking Through a Session Protocol (TTSP), served to facilitate the teacher's recognition of connections between her classroom and leadership practices.