The article proposes an approach to teacher development that situates learning in its context of development, with attention to what is learned, what tools are appropriated, and how teaching and learning are mediated in practice. The authors present the social design experiment which are cultural historical formations designed to promote transformative learning for adults and children, as a tool for imagining and designing robust learning ecologies. The authors illustrate how cultural historical concepts of learning and development and situated practice become the means for university students to gain distance and reflect on the beliefs and practices that have informed their understandings of teaching.