Recognizing that teacher leaders play an essential role in curriculum adoption and implementation, the Chicago Public Schools Department of STEM (Science, Technology, Engineering, and Math) partnered with Loyola University Chicago's Center for Science and Math Education to create a system of professional learning designed to advance teachers' practice while also explicitly enhancing their leadership capacity. A cornerstone of this effort was the science master teacher leader cohort, a group of science teachers in the district who worked collaboratively with the Center for Science and Math Education and with each other. With support from the Bill & Melinda Gates Foundation, the group built a program that addressed common gaps in the field by defining teacher leadership, attending to issues of diversity and equity, and detailing leadership preparation components (Wenner & Campbell, 2017). That effort is paying off in improved instructional strategies and teachers' leadership development.