Changes in society are inevitably reflected in changes in education and especially in school curricula. However change has also been acknowledged as difficult and one area where change is fiercely contested is in school curricula. Mandated change is often resisted and can be diverted from its original course. This book looks at the wide scenario of mandated curriculum change in the context of a specific subject. The development of a new physics curriculum and its implementation in schools are explored using in-depth interviews with the writers of the curriculum and teachers who were involved in the implementation. The rich experiential data is analysed using a sociocultural theoretical framework especially that of Etienne Wenger. Three key elements are identified as being critical to effecting any real change. A model of curriculum change based on the concepts of reification and dereification is developed. The descriptions, analyses, and theory in this book will be of value to education policy makers, curriculum developers, teacher educators and teachers themselves as they set out to make real changes in the classroom and not just on paper.