[Part I. General and theoretical issues, On the natural emergence of language structures in CLIL]
It is important to ensure that the implementation of modern European educational bilingualism be based on sound theoretical underpinnings. We discuss the development of L2 competence, as evidenced in sentence and text grammar, gauging the extent to which the incidental language learning favoured by a CLIL (Content and Language Integrated Learning) approach appears to satisfy the requirements of content learning. Secondary CLIL learners were given writing prompts designed to produce short passages of academic type language. The resulting texts are employed to discuss (a) the alignment of content and grammar and the primacy of semantic considerations; (b) transfer between L1 and L2 and the undeniable role of the L1, and (c) interlanguage levels and the need for realistic attainment models. They also serve to illustrate the importance of communicative need in CLIL-type approaches.