This article discusses how subject knowledge development should be conceptualised in the preparation of new secondary school teachers. It is written at a moment of national curriculum revision in England and a "knowledge turn" in education, bringing questions of subject knowledge development to the fore. The authors argue that the educational purpose of "subject knowledge" has been oversimplified and separated from teachers' concerns with pedagogy, performance and the child's experience. A new disciplinarity is needed in which the subject discipline becomes an overarching structure informing the teacher's curriculum thinking. However, the current, well-established model of the "good teacher" as skilled (and accountable) classroom technician fails to support such curriculum work. The authors propose that teacher preparation courses should develop a notion of the "good teacher" as engaged with the discipline as an educational resource. This article is conceptual, but draws from the authors' substantial experience of teacher preparation courses in secondary schools in England.