This research aims to discover which actions teachers adopt when pupils work cooperatively. 10 primary teachers' performance is analysed, through a qualitative design of observation of teaching practices in classrooms where cooperative learning is developed, complemented with the student teachers' perceptions. The results indicate a marked reduction in the interaction between the teacher and the whole class, with the focus changing from the traditional transmissive role of the teacher to one where, through alternative activities, the pupils become the protagonists. This change in approach to include active listening, scaffolding or immediate response to requests for help should be introduced in teacher training programmes to increase the willingness to use cooperative learning in classrooms.