Despite the widespread popularity of social networking sites (SNSs) amongst children and young people in compulsory education, relatively little scholarly work has explored the fundamental issues at stake. This paper makes an original contribution to the field by locating the study of this online activity within the broader terrain of social network theory in order to inform future educational debate and further research. The first section offers a way of classifying different kinds of online social networking and then places this within the context of the study of social networks. It is argued that relational networks create a sense of belonging and that online networks just as easily trace the contours of existing social divisions as they transcend or transform them. This analysis informs the second section which specifically addresses educational issues, including both the attractions and the limitations of such work. The paper concludes with an exploration of three possible approaches to using in SNSs in educational contexts. (Contains 1 figure.)