Student teachers in England, mainly on one-year courses, spend the majority of their time in schools. Secondary schools are primarily organised around subject departments, and these subgroups within schools have been shown to be significant for student outcomes and teachers' experiences. However, research on school subject departments themselves is relatively limited, and developing better understandings of school subject departments is important for Initial Teacher Education (ITE) and educational research more broadly. This paper draws on an ethnographic study of three secondary school geography departments to analyse student teachers' positionalities as knowers within departments. Opportunities for professional discussions within departments are limited, and are often dominated by immediate practical concerns. A social-realist concept of knowledge-knower structures is used to explore the kinds of knowers accepted as legitimate in these departments. A dichotomous view of teachers as knowers was found, being positioned as knowing or not-knowing particular areas of subject knowledge. This binary view is argued to be related to the language of the Teachers' Standards in England. Suggestions are made for improving student teachers' positions as knowers within departments by planning opportunities to contribute their expertise, and for developing more expansive discourses around subject knowledge to enable all to maximise opportunities to learn from the rich mines of expertise held across ITE partnerships.