Focusing on code-switching from conversation analysis and sociolinguistic perspectives, this paper examines interactions between 10-12-year-old language learners of immigrant origin and locally born students as they are engaging in verbal pair work. All are students attending language classes in state primary schools in Barcelona in which Catalan is the official language of the institution, Spanish is the common language of communication among students, and English is taught as a foreign language. By examining transcripts of recorded interactions between student pairs, we analyze the role played by Catalan and Spanish code-switching in the context of classes where students are studying Catalan and English. Our results show that language alternation serves to address practical issues related to the management and completion of the assigned pair activities. We will argue that, although code-switching is a resource available to students in multilingual contexts, rather than a distorting element, the implicit and non-implicit language policies in the classroom cannot be separated from the analysis of multilingual switches and the concept of plurilingual competence.