This quasi-experimental study was part of the SPRinG project (Social Pedagogy Research into Group Work). The review notes group work in "authentic" classrooms rarely fulfils its interactive or attainment potential. SPRinG classes undertook a programme of relational training to enhance children's group working skills while control classes maintained usual classroom practices. 980 children (38 classes) were studied over a school year. Interaction on a collaborative task, systematic work setting observations and reflective ratings of teacher actions were used to compare between SPRinG and control classes. Results show: SPRinG attainment was supported by increased engagement in group work, on-task focus, symmetric co-regulated communication and decreased social distraction. The study identifies enhanced reading/mathematics attainment in SPRinG classes. The teachers' role changed within SPRinG classes--becoming less directive and more supportive of group activity; but not all teachers acted in the same manner. Higher levels of implementation of SPRinG activities were associated with enhanced pupil dialogue and engagement. (Contains 9 tables and 1 note.)