This article reports on the results of a qualitative case study that addresses recent calls for greater attention to clinical aspects of practice and experiment in teacher education programmes. Grounded in the notion of approximations of practice, this study uses the analytic lens of teacher identity to understand how one group of preservice teachers in Hong Kong negotiated boundaries between opportunities for practising teaching within their university classroom and the classrooms of their practicum placement schools. Through in-depth interviews and classroom observations, this paper explores relations between opportunities to practice instructional routines and teacher identity construction within and beyond the university classroom. The data suggest that preservice teachers can face considerable challenges in constructing identities as they move between opportunities for practice available in coursework and engagement in the practices and activities of teaching within schools. These challenges include negotiating competency and gaining legitimate and legitimising access to practice as they confront relations of power within schools and teacher education programmes. Implications for the organisation of teacher education programmes that promote teacher agency and for future research are discussed.