Abstract The article addresses how heterogenous primary school students in Switzerland use learning opportunities to develop their English-speaking competences offered in Content and Language Integrated Learning (CLIL). Based on the lesson study approach, two task-based CLIL modules combining the subjects English and art were implemented in different primary classes with a focus on three case pupils in each class who represent high-attaining, average and low-attaining learners of English. Their spoken communication was analysed with an adapted version of the Communication Orientation of Language Teaching (COLT) observation scheme ( Allen et al., 1983 ) and according to the language triptych ( Coyle et al., 2010 ). Surveys were also conducted to investigate learners’ and teachers’ perception of the learning opportunities. The results indicate that the high-attaining and average students used the provided opportunities almost equally for developing their oral English competences. Although the low-attaining learners used the CLIL tasks in a significantly different way, they also achieved the objectives for speaking in English about art.