There's long been a cherished belief among some education reformers that student performance can be lifted by giving private school tuition vouchers to children stuck in low-performing public schools. That belief took a big hit last month, the latest in a series of big hits.

The U.S. Department of Education's research division released a report saying that first-year participants in the District of Columbia's Opportunity Scholarship Program did much worse in math than the kids who were denied a voucher and stayed in public school. Students from kindergarten through fifth grade also fared much worse in reading, and among older students, reading scores were close to those of their public school peers. The findings help debunk the notion that voucher-enabled students in private schools produce better outcomes than those attending public schools.

The Opportunity Scholarship Program is the nation's only federally funded voucher program. President Donald Trump and Education Secretary Betsy DeVos, a longtime voucher advocate, have proposed a national voucher program as part of a $1.4 billion education choice package, even as Trump proposes cutting the rest of the department's $69 billion budget by 13.5 percent. Trump plans eventually to spend $20 billion a year on school choice programs. But to win congressional approval, the administration must demonstrate consistently elevated performance results, which so far have been elusive.

Studies of statewide programs in Indiana, Louisiana and Ohio and in local districts in New York, Milwaukee and Charlotte, North Carolina, have found that giving low-income kids a private school option is not the solution some education reformers have claimed. A few students have done very well. Voucher students tend to go to college more often than those in public schools. Most students muddle along, and many get overwhelmed.

The quality of private schools has been an issue. The District of Columbia vouchers are good for $8,452 for elementary and middle schools and $12,679 for high schools, not nearly enough to cover tuition at the most prestigious schools. In Washington, about half of the 1,100 voucher students attend established parochial schools.

But in 2012, the Washington Post reported that hundreds of others attended unaccredited schools, such as a family-run K-12 school operating out of a storefront, a Nation of Islam school based in a former private home and a school built around the philosophy of a Bulgarian psychotherapist.

Lousy numbers haven't deterred voucher advocates. Last year, Sen. Ted Cruz, R-Texas, suggested requiring D.C. schools to grant vouchers to any child whose parents wanted one. "School choice is the civil rights issue of our era," he said.

Asked whether bad school choice programs could actually make things worse, DeVos responded, "Well, I'm not sure how they could get a lot worse on, you know, a nationwide basis than they are today."

Reformers should trust the data, not loosely grounded ideology.

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