In an era of prolific funding for varied small-school models, there is a growing emphasis on schools that alter the landscape of educational design. Some of these models attempt to redesign schools to place students at the center of learning and provide powerful examples of very different ways of thinking about teaching and learning (some examples include: Ed Visions and Expeditionary Learning Schools). Key to the success of these designs is the ability to build teacher capacity, or the "capacity to produce worthwhile and substantial learning", where the school defines what "worthwhile" and "substantial" learning looks like. Professional development to build capacity becomes central to the mission of the school and can highlight challenges for those attempting to improve capacity in a variety of other contexts. The purpose of this article is to: (a) describe The Big Picture's [BP] philosophy around teaching and learning, particularly as it relates to professional development; (b) examine data on teacher experiences of what it means to be a teacher at this unusual school and of learning, unlearning, and relearning in BP's professional development program; (c) explore the role of professional communities of practice in the process of learning, unlearning, and relearning; and (d) discuss the implications of this data for others engaged in school reform, teacher professional development, and building communities of practice. (Contains 3 notes.)