ABSTRACT : The purpose of this action research was to verify the effectiveness of cooperative learning in a heterogeneous group. It was conducted in a public school in the municipality of Marinilla; in a group of 45 students. This project had two stages: first a detailed observation of the English classes was done and an analysis of their development in depth. Second, the application of group and pair activities. The data collection tools used were weekly journals, interviews with students and collection of artifacts. Results demonstrated the benefits of cooperative learning during primary education as well as the cognitive and social skills developed during the implementations. Some drawbacks of cooperative work were found that could be investigated and improved in future actions.