In recent decades, child well-being has become a key political and academic issue that has gained importance both in public policy and in the social sciences. It has historically been associated with a number of social and political variables: parenting practices and parental investment; quality of home life; the development of digital tools; and, crucially, a child’s school experiences, which form the core of children’s daily lives. Initially defined negatively – that is, as an absence of health problems, illness, or feelings of failure or low self-esteem – well-being has come to be viewed as a more positive concept. This more positive definition has also attempted to take better account of the child not just as an adult in the making, but as a being “in the present” with needs and expectations different from those of an adult, in light of the advances and findings of the new sociology of childhood. In this introduction, we will review the questions raised by the issue of well-being at school, before presenting this book’s contribution to understanding it. This book aims to address several aspects of the global issue of child and adolescent well-being at school, articulating several of the dimensions and factors involved. It takes an international perspective, with chapters devoted to countries as diverse as the United Kingdom, the United States, New Zealand, Australia, Belgium, and, more broadly, Europe, while giving a central place to France, which poses a series of original questions in this respect. In the first section, we have grouped together the authors who approach child and adolescent well-being at school from the angle of public policy, be it educational policy in the UK or New Zealand, or early childhood care policy in Europe more generally. This first section provides the reader with an overview of the issues at stake in terms of public policy, from the ways in which governments in the UK and New Zealand have responded to what has been seen as a deficit in the well-being in newer generations, to the ways in which, on a European scale, an early childcare policy has been imagined as an equalizer of inequalities and an instrument for combating child poverty, the main obstacle to the well-being of the new generations. The second section of the book shifts the focus to the French case, and takes a closer look at the environment, that is, the everyday context where children live their lives. It brings together contributions that examine the role of school-family relations on the well-being of girls and boys, both in primary and secondary school. The focus on France is particularly interesting here, as it is characterized both by a major investment of public funds in its education policy and by a level of pupil achievement far below this investment when compared on an international scale (particularly in the OECD’s PISA surveys). The third section enters the school setting and looks more specifically at the (socially differentiated) way in which peer relations or student-teacher relations affect children’s level of well-being, at school and in general, – and in doing so, their academic success. Despite the diverse geographical areas studied (USA, the UK, France and Portugal), the three chapters in this section underline the importance of the school climate, particularly for children from working-class backgrounds or in precarious situations. What’s more, they highlight the unequal importance of peer sociability or relationship quality, which depends on the child's gender, social background, and geographical context, thus underlining the need for a multidimensional, contextualized approach to well-being or ill-being, whether in terms of research or public policy.