California is in the midst of a fundamental remaking of its assessment and accountability system that has been in place for 15 years. The state has the opportunity to play a leadership role in developing a multi-faceted assessment and accountability system that goes beyond a narrow focus on test scores and that could be a model for the nation. The transition offers California the potential to develop a more effective system that will not only assess students in more meaningful ways across more parts of the school curriculum, but also will provide educators with meaningful information about their students to help drive academic improvement. The purpose of this EdSource report is threefold: to clarify the timeline for the revision of California's current testing and accountability system; to identify essential principles that must be incorporated into the new system for it to be most effective; and to make recommendations to ensure that whatever new system is developed happens in a timely way, and is most likely to have its desired outcome of improving student performance.