This article reports on a school-based research project into teaching composing at GCSE, setting this alongside a review of the literature. It suggests that research into cognition in composing in school students and teaching composing within a school context may be synthesised by understanding composing as problem solving. Composing is described as knowledge-rich, complex, multiple and creative problem solving, requiring the development of skills of hypothesis and verification in students. A series of case studies of individual teachers is analysed using Bernstein's framework for coding knowledge in the curriculum. Research data presented suggest that although there is significant variation in the practice of individual teachers, teaching composing is characterised in the main activities of instruction and training in composing skills and knowledge; management of a positive creative learning environment; and facilitation of ownership, autonomy and authority in students. The article concludes by suggesting that conceptualising teaching composing as problem solving enables music educators to rationalise the specific demands of the curriculum context in which they are operating by providing students with a framework for cognitive development in composing.