This guide describes the measures California state officials use to evaluate schools and school districts, explaining what they are and what they indicate. Results of standard tests and the Academic Performance Index (API) indicate substantial gaps between the achievement of various groups of students in California. African American, Latino, and Native American students; English learners; students who are socioeconomically disadvantaged; and Special Education students are all less likely to score proficient on state tests. The same gap exists in dropout and graduation rates. Because of limitations in its current data system, California is unable to answer many questions about student performance, and is also unable to accurately track a group of students over time. The state is working on a new data system, but it will be at least a year and probably longer before it is used for any of these purposes. (Contains 3 figures.)