Do school choice vouchers work? According to a new study, the answer depends on how many students using them private schools admit. 

The analysis of the data, published Jan. 28 in The Wall Street Journal, found that more successful voucher-using students could be found in Milwaukee private schools — some of them Catholic — that worked to balance the percentage of paying students and voucher students. 

Milwaukee schools in the top quartile for math and English state proficiency test scores had an average voucher enrollment of just over 50 percent, according to the study. Schools with scores in the two bottom quartiles had an average voucher student enrollment of more than 90 percent. 

“Schools that have 20 percent to 30 percent voucher kids and 70 percent to 80 percent fee-paying kids, they look more like the private schools that we sort of put on a pedestal,” private-school choice expert Patrick Wolf told the Journal.