As California approaches a new system of academic standards, instruction, and assessment, it enters familiar territory. The use of multiple modes of assessment, tight alignment between assessments and expectations for student learning, and a focus on assessment for formative (as well as summative) purposes—all with an emphasis on students’ understanding and ability to apply their learning—mirror the state’s priorities as it transitioned to the California Learning Assessment System (CLAS) in the early 1990s. These policy and practice briefs examine the CLAS experience to identify lessons for districts as they implement the Common Core today. Through these lessons, districts across the state might build on promising practices from two decades ago while avoiding some of the pitfalls that undermined the CLAS effort. These briefs were an outcome of the California Collaborative meeting Digging Into the Standards: Assessment and the Common Core.