Group work is generally accepted as part of the educational ideology of today's primary classrooms. It can, however, mean almost anything from group seating as a technique of classroom management to fully collaborative learning. The authors start from the position that getting children to work together is time-consuming and not easy and that teachers need some assurance that it is worthwhile. Drawing on the work of Vygotsky they look at the importance of collaboration in the development of higher mental functions and also discuss the social and emotional advantages that children can derive from working together. Also using case studies derived from the ORACLE II group work project at Leicester, the authors also take into account the advances made in collaborative group work in other countries. The result is a set of guidelines from which individual teachers can derive policies suitable for the circumstances in their own schools.