This book contains a report of a study commissioned by the California Legislature to examine charter schools in the state. The study considered the following four questions: (1) What population of students attends charter schools? (2) Is student achievement higher in charter schools than in conventional public schools? (3) What oversight and support do the chartering authorities provide? and (4) How do charter schools differ from conventional public schools in terms of their operation, including finances, academic environment, and staffing? Data for the study were gathered from surveys of principals in all charter schools, from a demographically matched subset of conventional public schools, from a survey of chartering authorities, from case studies at nine charter schools and all but one other chartering authority, and from a number of databases. The study found that charter schools are not homogeneous; they vary along a number of dimensions. There is no single charter-school effect. These differences affect accessibility, achievement, operation, and governance. The report includes a number of recommendations for policymakers. Appended are the research methods and instruments used in the study, a table of academic outcomes at charter schools, and a discussion of charter and conventional public-school comparison methods. (Contains 36 figures and 54 tables.) (WFA)