While the rhetoric of lifelong learning is now well established in government policy documentation, understanding how this is realized is less clear. For many primary school teachers mathematics is a subject that causes concern - its place within their personal biographies may be uncomfortable and replete with memories of confusion, pain and limited success. Professional understandings of mathematics build upon the understandings from personal histories. Discussing teacher change within such a complex environment is inherently difficult. Responses to this difficulty have tended to take the form of simplifying the task - paring away some of the complexity - either by ignoring subject matter and considering general pedagogy, or by focusing exclusively on subject matter shorn of the context within which it is taught. This book develops a framework within which to discuss primary school teachers making changes to their understandings and practices. The framework has been developed precisely in order to allow the complexity of the internal and external aspects of change processes to be explored in a holistic way. While the context of the book is time specific and it relates to a period