For years, the alternation between the L1 and the L2 was banned in language classes, since it was thought that this would impair the learning of the second language. In recent years, however, there has been a recognition of the validity of alternation. That is why this book aims at investigating the alternation of the L1 and L2 in Content and Language Integrated Learning (CLIL) and English Medium Instruction (EMI) contexts at three educational levels (primary, secondary, tertiary) in Italy. To do so, an overarching qualitative research approach was applied with both quantitative and qualitative elements. The results of the study point at three main pedagogical implications, which highlight the originality of this research. The first implication is connected to the function of alternation between the L1 and the L2. Alternation played a mainly lexical role to explain specific lexis or at least to provide the students with lexis in both languages (English and Italian). The second implication highlights the fact that despite the contextual differences that exist, the three educational levels (primary, secondary and tertiary) show a very similar use of alternation, thereby pointing at similarities more than differences. The third implication worth noting is the drive toward and preservation of multilingualism that comes from the use of alternation.
