As the internationally benchmarked Common Core State Standards, or CCSS, are adopted in states across the country, educators are seeking ways to support an increasingly diverse student population to meet these more demanding expectations. The likelihood that students will achieve the aims of the standards will be substantially shaped by how well teachers teach these challenging academic skills in ways that support a wide range of learners. Teachers’ understanding of the standards and their grasp of how to teach them will also influence whether the new assessments provide useful insights, rather than harmful side effects, particularly for those students who have historically been least well-served by their schools. This report describes how teacher learning through involvement with student assessments has been accomplished in the United States and around the world.