This study is an exploration of the ways in which experienced mathematics teachers recognize and learn about issues that shape their own professional practice. In a school-based professional development program teachers collaboratively analyzed their teaching practice in order to recognize and interpret concerns and teaching needs, as well as link them with corresponding decision making and teaching actions. Findings indicate that by systematically “unpacking” teaching and students learning and making rationalizations about their practice explicit, the teachers came to articulate, re- interpret and challenge what they need to know about teaching in order to orchestrate meaningful classroom practice.