Maurice Galton & John Williamson 
Group Work in the Primary Classroom [PDF ebook] 

Drawing on the work of Vygotsky, the authors look at the social and emotional advantages children can gain from working together. They use case studies derived from the ORACLE II group work project at Leicester, and also take into account the advances made in collaborative group work in other countries. The result is a set of guidelines from which teachers can plan policies suitable for their own schools.