Serbia has a network of eight educational institutions (one primary school and seven high schools) offering a French bilingual education. The bilingual sections have been developed since 2004 in seven towns throughout Serbia. In this form of enrichment bilingual education program, at least four non linguistic disciplines are taught in both Serbian and French, in addition to the standard teaching of French as a foreign language. In such a context, the issue of the articulation between both the languages comes up to the front, as part of a process of integration of linguistic knowledge and subject specific knowledge in the teaching of non linguistic disciplines. This article reports on the results of an exploratory research on code-switching in three non linguistic disciplines courses in a bilingual section in Belgrade. The analysis of forms and functions of code-switching in teacher’s and learner’s speech allow us to highlight several trends in teaching practices at the level of code-switching and code-mixing : these trends reveal didactisation of code-switching marks in teacher’s speech according to the courses formats, the types of activities, and the pedagogical objectives being pursued. It also reveals several factors which potentially impact on the operating field of code-switching in the perspective of a differentiated strategy being adjusted to learner’s needs.