This case study explores the motivations for code switching (CS) in the interactions of Tunisian students at the faculty of Economics and Management in Sfax, Tunisia. The study focuses on students' (EMSs) classroom conversations and out-of-classroom peer interactions. The analysis of the social motivations of EMSs' CS behaviour shows that classroom conversations are teacher controlled and that CS instances are mostly uttered for clarification or to enhance participation. The switches are motivated by the students' low abilities in French enhanced by the unstable linguistic situation of Tunisia after the Arabisation process. However, out-of-classroom conversations are mostly uncontrolled, unless in the presence of out-group members. All types of CS encountered explain the motivations for the emergence of an unconscious monolect as a means of interaction among in-group members. This monolect is set to achieve communicative goals where more importance is given to the message and less significance to the code. (Contains 2 tables and 2 footnotes.)