The paper illustrates how interaction operates in classes where there is no single shared common language between teachers and pupils. Samples from a European School primary class taken from 1669 extracts are given of teacher-pupil, pupil-teacher and pupil-pupil interaction. Goals of the programme investigated are to integrate heterogeneous groups while showing respect for language diversity, to encourage co-operation, to accustom pupils to a multilingual environment and to encourage development of multilingual skills. Communication strategies, both verbal and non-verbal, in a typical classroom sub-culture are shown. Results reveal how the strategies used by all involved enable them to cope with the unexpected, which is typical of a linguistically mixed class. Code-switching plays a significant and legitimate role in the coping strategies.