This chapter presents and discusses the third and final correlated strategy, that of implementing Content and Language Integrated Learning (CLIL) as part of the second-level education system. Through CLIL, students would receive even greater exposure to their additional language by undertaking part of a content subject (e.g., Maths) through their modern foreign language (MFL). The strategy could support students in achieving their expected CEFR B1 level (given number of MFL tuition hours provided), and it may even help many students obtain a low B2 level or higher. This chapter explores CLIL as an approach to foster plurilingual students; it presents a candid appraisal of CLIL, which is too often lacking in literature and reports; and it examines the European Schools system’s CLIL programme and how it operates in an effective manner to support the plurilingual development of its students. The chapter also reviews pilot CLIL projects undertaken in Ireland. The case is made for the initial implementation of a partial CLIL programme as a complementary strategy to cross-age teaching (strategy one). The findings from the empirical research conducted in Ireland (MFL students, teachers, school leaders, parents, and other stakeholders), as well as in the European Schools system are presented. A series of recommendations for the implementation of a partial CLIL programme is put forward.