Many policy and practice initiatives that aim to prevent social exclusion focus on children and young people. This book seeks to consider new approaches to understanding the complexities of prevention, and how these new understandings can inform policy and practice. The authors use evidence from the National Evaluation of the Children's Fund to illustrate and explore the experiences of children and families who are most marginalised. They consider the historical context of approaches to child welfare, and present a new framework for understanding and developing preventative polices and practice within the context of social exclusion. Preventative initiatives such as the Children's Fund have supported large-scale complex evaluations that have generated rich and important data about strategies for addressing social exclusion and what they can achieve. The findings of this book have direct relevance for all those engaged in developing preventative policy and practice and will therefore be of interest to policy makers, practitioners and students of child welfare and social policy more broadly, in providing a timely discussion of key debates in designing, delivering and commissioning preventative services.