IMAGINE you are a poor parent in Washington, DC. You assumed you would send your child to a public school. But you have been offered a voucher worth up to $12,000 towards tuition at a private one. Should you use it?
Until recently the evidence suggested that you should. In 2004 Congress created the DC Opportunity Scholarship Programme, the first school-voucher scheme directly subsidised by the federal government (states and charities subsidise many others). Since then up to 2,000 families a year have been handed vouchers to attend private school after winning lotteries. In 2010 a study found that 82% of pupils offered a voucher went on to graduate from high school, compared with 70% of similar peers who attended public schools.