Over the course of six years, a diverse group of school districts and charter management organizations in California ran a substantial experiment in implementing the Next Generation Science Standards (NGSS) in elementary and middle grades. WestEd led an extensive evaluation of that effort, the California K-8 NGSS Early Implementers Initiative, resulting in more than a dozen evaluation reports highlighting important themes and learnings. All reports are intended to be helpful to administrators at the school and district levels, education policymakers, and people charged with designing and/or delivering science professional learning. This report on highlights from the Early Implementers Initiative is the final report of the series. It offers high-level, major lessons learned, challenges, and strategies gleaned from the evaluation series. It also offers recommendations for policymakers and administrators for implementing the Next Generation Science Standards in their own districts.