This "ERIC Digest" considers the U.S. charter-school movement, which has produced about 800 schools in half the states and enrolls over 100,000 students. Charter schools reflect founders' varied philosophies and commit to achieve certain educational outcomes within a certain period, in exchange for waiving many restrictive regulations. If outcomes are not met, charters are revoked by sponsors. Rooted in recent reforms, charter schools are viewed by many as a workable political compromise and alternative to vouchers. Stressing autonomy and accountability, the charter approach uses market principles while upholding democratic, nonsectarian philosophies. State laws follow organizing principles based on Minnesota's pioneering efforts, American Federation of Teachers guidelines, and/or federal charter-school legislation. Preliminary research shows that charters are generally small, new, racially diverse schools that appeal to students, parents, and teachers who had disappointing experiences elsewhere. Charters' chief implementation obstacles are funding and school-system opposition. Charter legislation is more likely in states with a policy entrepreneur, poor test scores, Republican legislative control, and proximity to other charter-law states. Unions, private management companies, and school superintendents are starting charters or using them to improve the larger system. (Contains 10 references.) (MLH)