In this chapter we discuss the nature of children's achievement motivation and how it develops over the school years. We focus on the competence-related belief, value, goal, interest, and intrinsic aspects of motivation that have been emphasized in much of the research on motivation. We then discuss how different aspects of classroom and school practices influence motivation, and how teacher–student relationships and peer relationships impact students’ motivation. We next consider how school transitions influence students’ motivation, describing important differences in the structure and organization of schools at different levels of schooling. In the final section we describe some recent intervention work to boost children's motivation in different ways. Suggestions for future research include how students’ motivation varies in different classroom contexts, the need to study motivation in diverse groups of children, methodological issues with respect to studying motivation, what other kinds of further motivation intervention studies are needed, and how work on motivation can inform educational policy.