This paper explores the effects of enacting a collaborative and enquiry based model of teacher professionalism in the UK. Based on work with Chartered Teachers in Scotland, it indicates that the barriers to changing the basis of teacher professionalism are complex and multi-faceted because of the contested nature of teachers' work identities. Chartered Teacher status is achieved by qualification against an occupational standard which positions those who attain it as leading teachers, exerting a significant influence with their colleagues to improve the quality of teaching and learning in schools. This paper looks at some of the conceptual and practical difficulties faced by Chartered Teachers as they try to enact what this new "status" means. It argues that those with an interest in the professional development of teachers need to position themselves as knowing agents in the complex systemic and political aspects of changing practice in schools.