The two insights behind school choice are that externalities motivate government financing, but not provision, of schools, and that government-run schools will probably, owing to lack of competition, be x-inefficient. Under school choice, students choose among schools that compete for them on a truly level playing field. Governments play a financing, auditing, refereeing, and market-design role. Modern research focuses on evaluating the effects of school choice on the x-efficiency of schools, analysing how programme design affects the supply of schools, and investigating how information and matching mechanisms affect demand.