Findings from two studies are discussed in relation to the experiences and challenges faced by teachers trying to implement effective group work in schools and classrooms and to reflect on the lessons learnt about how to involve pupils with special educational needs (SEN). The first study reports on UK primary school teachers' experiences of implementing a year-long intervention designed to improve the effectiveness of pupils' collaborative group-working in classrooms (the SPRinG [Social Pedagogic Research into Group-work] project). The second study (the MAST [Making a Statement] project) involved systematic observations of 48 pupils with SEN (and comparison pupils) and case studies undertaken in the context of primary school classrooms.