"Do School Vouchers Work? Milwaukee’s Experiment Suggests an Answer" from The Wall Street Journal
MILWAUKEE—Almost three decades ago, Milwaukee started offering the nation’s first-ever school vouchers. Starting small, the program allowed poor children to use taxpayer money to attend private schools. Today, about a quarter of Milwaukee children educated with public funds take advantage, making the program a testing ground for a big experiment in education.
Did students in the program get a better education? That depends on how participating schools handled a critical issue: how many voucher students to let in.
A Wall Street Journal analysis of the data suggests vouchers worked best when enrollment from voucher students was kept low. As the percentage of voucher students rises, the returns diminish until the point when there is little difference between the performance of public and private institutions. The vast majority of private schools participating in the program today have high percentages of publicly funded students.