It is commonly understood that policy makers make curriculum policy and teachers implement it. Some teachers, however, have been in on the ground floor of curriculum policy development. Driven by events in their life histories and teaching contexts, these teachers develop and teach original course material in their own classrooms. Over time they begin to work collaboratively on further course development, secure organizational support to ensure adequate resources and legitimacy to disseminate these new curricular forms, lobby for course acceptance by educational jurisdictions, and help establish course infrastructure such as teacher professional learning opportunities and textbooks. In other words, in some cases, teachers may participate actively in every stage of policy development and practice. This article discusses the phenomenon of teacher-driven curriculum innovation as a process of individual, social, and political evolution. It describes three cases of secondary-level courses developed by teachers in Ontario, Canada, and formalized in district or provincial policy. In doing so, the article extends the notion of teacher agency from its established arenas of classrooms and schools and into the realm of policy making.Most educational research describes teachers' involvement with curriculum as limited to their own classroom teaching. This article presents three recent examples of curriculum development where teachers have been major drivers in changes to policy and practice well beyond their classrooms and schools.The teacher-driven curriculum development described in this article often starts with small numbers of teachers working independently on new content or pedagogical approaches. Their work is further developed and spread through collaboration with other teachers as well as academics and other community members. This expansion is aided by the involvement of subject associations, teacher unions, formal and informal networks, university departments, school districts and nongovernmental organizations, which provide both the resources and credibility necessary to bring these bs_bs_banner