To introduce this special issue, the concept of the teacher as an ''invisible hand'' is presented as a metaphor to describe the potentially influential but relatively understudied contribution that educators are likely to have on children's peer relationships and their broader interpersonal growth. Building from conceptual work distinguishing between the role of adults and peers in children's social development, we summarize empirical support for the view that teachers are in a position to develop and guide the classroom as a society by simultaneously directing institutional expectations while also providing students with opportunities to collectively construct their own peer culture. Key social development constructs are reviewed from this lens, and the four articles and two commentaries that constitute this special issue are discussed in relation to their contributions to clarifying and extending current views of the role of teachers in school social dynamics. We conclude by considering intervention implications of this work, and we argue that teachers are the one professional in a child's life who have the opportunity to view the whole child in relation to the social ecology in which he or she is embedded.