A new report from the Century Foundation’s Halley Potter tackles this claim, examining the empirical effects of private-school vouchers on different forms of segregation. According to Potter, “The academic results of private-school voucher programs thus far have been disappointing.” In all likelihood, vouchers will lead to more racial, religious, and socioeconomic segregation in schools. Potter’s report finds that many voucher programs fail to deliberately target low-income students, which can increase the concentration of wealthier students in private schools. In addition, religious students on vouchers often transfer to private parochial schools, contributing to religious homogeneity at these institutions and limiting opportunities for religious diversity at others.

A larger focus of the report is the impact of voucher programs on racial integration. In particular, Potter examines two U.S. studies, one in Louisiana and the other in Milwaukee, which each tracked students who moved from public to private schools. The first study, published in 2016, looked at the Louisiana Scholarship Program, a statewide voucher program that targets low-income students at low-performing public schools. The study originally reported that while public-school segregation decreased significantly, private-school segregation was somewhat higher. Potter found these results misleading for two reasons: First, the loss of a few students from overrepresented groups at public schools had a small effect on overall demographics. Second, the study reported the effects of voucher transfers on public and private schools separately. After crunching the numbers herself, using metropolitan demographics as a benchmark for integration, Potter’s results were quite different: Two-thirds of the school transfers had negative or mixed effects, resulting in overall increased segregation.

The second study, conducted in 2010, examined the transfer of students using the oldest school-voucher program in the country, the Milwaukee Parental Choice Program. As of the 2008-2009 school year, around 80 percent of students using these vouchers were black. According to Potter’s analysis, nearly 90 percent of the program’s students transferred from a public school where they were in the majority to a private school where they were still in the majority. This meant that although schools did not become more segregated, they also did not become significantly integrated.

Together, these studies indicate that private-school vouchers do not promote racial integration. In fact, contrary to DeVos, Potter finds that school diversity and voucher programs are often incompatible, primarily because students are moving in a one-way direction from public to private schools. “If you’re taking a commitment to school integration seriously, then private-school vouchers are not an effective way to achieve that goal,” Potter says.