Every year we invest billions in professional development to build teachers' capacity to better address the diverse academic needs of every student. Yet student learning continues to fall short of expectations in too many places. We must ask the question: Is there a better way to invest in the professional learning of teachers across America? Our answer is an emphatic yes. NIET has spent 20 years building the capacity of teachers and school leaders. We have seen that professional learning is best led by teachers and leaders within the school building. Funding flexibility under the Every Student Succeeds Act (ESSA) offers a renewed opportunity to fund teacher leadership as a strategy for schoolwide instructional improvement. In this report, we provide recommendations that leaders at district, state, and federal levels can use to align funding and practices to invest in building the instructional capacity of teachers through professional learning led by teacher leaders.