What's more, there have been 10 random assignment studies of school vouchers (the best design possible) and 9 of them have found positive results for some or all participating students. (educationnext.org)
Which random - assignment study of small schools showing negative results did I leave out? (jaypgreene.com)
For the first time ever, a random - assignment study found a negative result from a school voucher program. (educationnext.org)