This study concerns the purposes of music education in English secondary schools at key stage 3 (age 11-14) and the role of music educators: whether it is to provide an experience of music or whether it is to develop musicianship in young people; how far teachers understand what it is to be musical and how musicianship can be developed. Music teachers will come from a range of diverse backgrounds, though research data would suggest that most seem to have been educated as ‘classical’ music performers which will have an affect on what they perceive to be central competences in the development of musicians. In turn, this will determine, to some extent, what is taught and learned in the classroom, as tensions can frequently arise between teachers’ expertise and the musical interests and needs of their pupils. This study explores how far the biography of secondary music teachers determines the approach they take to musicianship and the activities which are presented to young people in the classroom. A mixed methods approach has been taken which has focused principally on the competencies and learning contexts required for the development of musicianship and how far these have been observed in practice in the classroom. The outcomes of the study have suggested a clear link between teacher biography and classroom practice but that there are potential tensions which can arise out of school practices, national policy, curricular organization, teachers’ education and training, and the musician-teacher identity. The study concludes by suggesting a range of recommendations for action to the ‘stakeholders’ responsible for the delivery of music education in English secondary schools.