Research has shown that learning to teach mathematics for understanding is not simply a matter of learning new pedagogical techniques but rather requires substantial changes in a teacher's knowledge, beliefs, and practice (Putnam and Borko 2000). Preparing teachers to implement reform-oriented curricula requires positioning them as learners and inquirers of mathematical content, student learning, and instructional practice. Ball (1996) asserts that teacher professional development must embrace the uncertainty of practice and reflect a “stance of critique and inquiry—a stance of asking and debating, a discourse of conjecture and deliberation” (p. 506).