In this chapter we have looked at the concept of children’s development during the school years, with a particular focus on cognitive, language and social skills. Specifically, we have examined what factors influence children’s development as they enter school. We have discussed cognitive development during the school years and considered the implications of Piaget’s and Vygotsky’s theories for understanding children’s learning. The chapter has focused on how children develop language, theory of mind and social reasoning during the school years, all of which are important skills for later development and social interactions. We have also discussed aspects of children’s development within the context of school, including the importance of cultural tools and classroom-led instruction, and have focused particularly on early reading development and mathematical understanding. Finally, the chapter reviewed the changing dynamics of children’s social world as they enter school by discussing school adjustment, socialisation and friendships, and the development of moral understanding. All of these topics emphasise the relative importance of the social context in explaining and understanding children’s development in the school years and reinforce the argument that development can only occur through a child’s interaction with their social environment.