Inquiry-based curricula are an essential tool for reforming science education yet the role of the teacher is often overlooked in terms of the impact of the curriculum on student achievement. Our research focuses on 22 teachers' use of a year-long high school urban ecology curriculum and how teachers' self-efficacy, instructional practices, curricular enactments and previous experience impacted student learning. Data sources included teacher belief surveys, teacher enactment surveys, a student multiple-choice assessment focused on defining and identifying science concepts and a student open-ended assessment focused on scientific inquiry. Results from the two hierarchical linear models indicate that there was significant variation between teachers in terms of student achievement. For the multiple-choice assessment, teachers who spent a larger percentage of time on group work and a smaller percentage of time lecturing had greater student learning. For the open-ended assessment, teachers who reported a higher frequency of students engaging in argument and sharing ideas had greater student learning while teachers who adapted the curriculum more had lower student learning. These results suggest the importance of supporting the active role of students in instruction, emphasising argumentation, and considering the types of adaptations teachers make to curriculum.