How do educators at a systems level know that professional learning is impacting teacher practice in a way that leads to improved student outcomes? California's Long Beach Unified School District, a member of Learning Forward's Redesign PD Community of Practice, partnered with other districts from across the country to answer that question. As educators in the district clarified their understanding of evaluation and developed tools to better measure impact, partner districts provided critical and constructive feedback to help them refine their work.