High-stakes testing gets a lot of criticism, for good reason. But, when done right, assessment can be a valuable tool for educators and students. Kim Marshall describes how different types of assessments can improve learning by revealing learning problems in real time, improving student retention through the "retrieval effect," and enabling teachers to leverage peer instruction. They can also be used to promote a growth mindset by giving students ways to see and monitor their own progress. Conversation with schools will more easily shift to learning results and prevent knowledge and skill gaps as teachers collaborate around assessment results and school leaders become more aware of where students are.