In this article an exemplary analysis focussing on the role of multilingual communication in upper secondary education at a German school will be presented. In the analysis, we focus on the language choice of two pupils who, during partner work on the analysis of a historical speech in History class, use both the German and Russian language. We reconstruct extracts of their task solving process in the context of a functional-pragmatic discourse analysis. The excerpts of the partner work presented in the text show approaches of multidimensional reflection processes in working with the text, during which it comes to a functional use of both languages. The relevance of our reconstruction of student-student interaction during task solving will become evident through the embedment of the results in the controversial discussion on multilingual communication in mainstream classrooms.