Luxembourg is a trilingual country where residents communicate in Luxembourgish, French and German concurrently. Children therefore study these languages at primary school. In this paper I explore how six eight-year-old Luxembourgish children use and learn German, French and English in formal and informal settings over a period of one year. Their eagerness to learn and use German and English contrasted with their cautious and formal approach to the learning of French. My findings demonstrate that second language learning in a multilingual country is not an "automatic" or "natural" process but, rather, children's language behaviour depends on their personal goals, interests, competence, confidence and understanding of what counts as appropriate language use. These factors are influenced by the formal approach to language learning at school. (Contains 2 tables, 4 figures and 1 note.)