This book uses Vygotsky’s cultural-historical theory to provide a unique theorisation of teachers’ professional development as a practice. A practice can be described as the socially structured actions set up to produce a product or service aimed at meeting a collective human need. In this case, collaborative, interventionist work with teachers in two different Australian primary schools sought to simultaneously identify, understand and develop the necessary conditions for supporting the teachers’ development as professionals. The in-depth analysis of this practice provides interesting insight into professional development for teachers at all levels of schooling, and provides strong support for educational researchers, administrators and consultants to reconsider many existing forms of professional learning/development programs. This book supports the contemporary view that professional learning must take place with teachers, rather than be delivered to teachers, but provides an important expansion to current work in this area by arguing that a focus on teachers’ learning of new strategies and principles may still fall short of creating long term change in teachers’ professional practice. By taking a cultural-historical approach, the focus moves to supporting teachers’ development of unified concepts (the intertwining of theoretical and practical aspects) and motives to continue their ongoing development as professionals. This emphasis builds teachers’ capacity to examine and disrupt habitual practices and understand, create and implement thoughtful and sustainable transformations in all areas of their professional life. This book therefore builds upon the ongoing conversation about professional learning and development, offering a new framework for researching, understanding and developing this critical practice.