Urban school districts face a dilemma in providing professional development support for teachers in transition to the Next Generation Science Standards (NGSS). Districts need to maximize the quality and amount of professional development within practical funding constraints. In this paper, we discuss preliminary results from a researcher-practitioner partnership between Northwestern University and the Chicago Public Schools. We explore a model for quarterly NGSS professional development for urban middle school science teachers that spans three years. The workshop inquiry experiences are aligned to areas of research excellence at Northwestern. Teachers in twenty-three of the schools responded to a survey on the impact of formal and informal learning experiences on changes in teaching practice. We also analyzed the growth in student-rated inquiry-based science teaching practices. The results indicate that the professional development program had a significant direct impact on teaching practices as well as indirect impact on the teaching practices of other teachers at the school.