School choice and school competition: Evidence from the United States, a recent study by Caroline Hoxby, opens with this abstract:
The most frequently asked questions about school choice are: Do public schools respond constructively to competition induced by school choice, by raising their own productivity? Does students? achievement rise when they attend voucher or charter schools? Do voucher and charter schools end up with a selection of the better students (?cream-skim?)? I review the evidence on these questions from the United States, relying primarily on recent policy experiments. Public schools do respond constructively to competition, by raising their achievement and productivity. The best studies on this question examine the introduction of choice programs that have been sufficiently large and long-lived to produce competition. Students? achievement generally does rise when they attend voucher or charter schools. The best studies on this question use, as a control group, students who are randomized out of choice programs. Not only do currently enacted voucher and charter school programs not cream-skim; they disproportionately attract students who were performing badly in their regular public schools. This confirms what theory predicts: there are no general results on the sorting consequences of school choice. The sorting consequences of a school choice plan depend strongly on its design.