This book develops a framework for discussing primary school teachers making changes to their understandings and practices. The framework has been developed to allow the complexity of external and internal aspects of change processes to be explored in a holistic way. External factors influencing teachers include increased specification of the curriculum, changing demands for styles of pedagogy and a rhetoric of Lifelong Learning. Such factors have to be looked at in relation to individual teacher's internal responses to mathematics. 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 the interplay of the external and internal is inherently difficult. Responses to this difficulty have tended to take the form of simplifying the task and dealing with the external separately from the internal. This book will be of interest to a wide range of people working in the field of primary mathematics education, including policy makers, Initial Teacher Education lecturers, Master's students and researchers, practising primary school teachers and those engaged in the management of mathematics in primary schools. While the context of the book is specific to a period of time when a National Numeracy Strategy was being introduced into schools in England, the themes that the chapters tackle are broader and consider issues of interest to anyone concerned with the development of mathematics teaching.