This article employs the concepts of "professional jurisdiction" and "formal knowledge" to examine threats to teacher professionalism in England arising from the British government's "workload remodelling" policy to expand the numbers and remit of staff in schools without qualified teacher status. The connection between knowledge and professional control is discussed. It is argued that the lack of a codified body of knowledge for teachers may ultimately cause the erosion of teachers' professional jurisdiction in English schools and a downgrading of their status. The repercussions of this for school leaders and managers and the wider implications this case study has for the sociological study of the professions are discussed. The first part of the article will seek to map a broad theoretical framework in which to contextualize the connection between knowledge and professional control. The subsequent sections will argue that, because there is no codified body of teacher knowledge, the profession lacks convincing arguments against the expansion of the role of non-qualified teaching staff and that, ultimately, we may see a further erosion of teachers' professional jurisdiction in English schools and an associated downgrading of teachers' status. A final section examines some of the repercussions of this for school leaders and managers and notes the wider implications this case study has for the sociological study of the professions.