Teaching students how to conduct authentic scientific inquiry is an essential aspect of recent science education reform efforts. Our National Science Foundation-funded GK-12 program paired science graduate students--fellows--with secondary science teachers in order to enhance inquiry-based instruction. This research examined the roles of the fellows, teachers, and school culture in the implementation of inquiry and the fellows' conceptions of classroom inquiry versus that in their own research. Qualitative data were collected for two academic years. Overall, the classrooms shifted toward a more inquiry-oriented approach over the academic year. Several aspects of school culture influenced inquiry implementation. Fellows described their research as similar in overall structure but less constrained by known concepts, less guided by mentors, and more in-depth than that of secondary school students. The teacher-fellow scientist partnership is a potentially effective professional development model to create positive and lasting change within the science classroom.