This article is concerned with the conditions and stakes of building competence in multiple languages in learners who, due to their language biographies or the educational system, are studying in prestigious institutional school environments, such as the French–German schools of Buc (Versailles), Freiburg (Breisgau) and Saarbrücken (Saarland). In particular, the research examines the reciprocal interactions between social representations of bi/plurilingualism and contexts of acquisition as the students integrate themselves within these institutional settings. We reviewed the conditions in which the data collected lead us to conclude or to infer changes in learners’ representations related to the languages and their language-learning experiences as well as their accumulation of knowledge. First, based on a qualitative and quantitative analysis of data elicited in the form of questionnaires and semi-structured interviews, we aimed to define the concept of plurilingual competence, which is heterogeneous in nature. This competence exists on two levels: first, on the macrolinguistic level, from the perspective of the organisation of curriculum and of individual trajectories of learning and, second, on the microlinguistic level, in its discursive and interactional reality in the learners’ plurilingual language practices. With this aim, the study began by investigating the content and the discursive processes of the development of representations by considering the dynamics of their structural and argumentative components. During the next stage, we analysed (using speech analysis tools) discursive practices such as language activities, which are situated in the interaction and contribute to the development and mutual construction of representations of plurilingualism. The study used tools of content and discourse analysis for didactic purposes. We have tried to reveal how the complex plurilingual language repertoire of French–German learners takes shape, through typological profiles and examining the constituent components of representations of identity and plurilingualism. Finally, in an active research mode, we suggest possibilities for future research on the didactics of plurilingualism and ways to rethink ‘multilingualism’.