Viewpoint: No, Private Schools Aren't Worse
Opponents of school choice have released a study claiming that students in Cleveland's public schools actually perform better than those who used a voucher to attend private schools. Unfortunately, this study is seriously flawed. What's more, school choice is supported by a much larger body of much better studies.
The study looked at Cleveland's ten-year-old voucher program. Using a new statistical model to analyze a previously existing data set, it found that kids remaining in Cleveland public schools do better than voucher users.
The data set used in this study, which has been used for several previous studies of Cleveland's program, does not allow for valid comparisons between similar student populations. The voucher students and the public school comparison groups are dissimilar not only because one group uses vouchers and the other doesn't, but also in a host of other ways, so there's no way to disentangle what's really causing the test score difference. The study compares apples and oranges.
The data compare voucher users to 1) all Cleveland students, and 2) students who remain behind in the schools that voucher users left. Comparing voucher users to all Cleveland students is clearly inappropriate, since the average voucher student is much more disadvantaged than the average student in the general Cleveland population. Voucher students start from way behind the average, both because they're socially disadvantaged and because they're coming from the worst schools in the public system.
Comparing voucher students to students in the same schools they left is not quite as blatantly outrageous, but it is still not a valid comparison. For one thing, those who stay behind are different from voucher users simply because they chose to stay behind when they could have used vouchers. Maybe that public school is a better fit for them than it is for the voucher students. A fair evaluation of the effects of school choice must compare outcomes for students who choose their schools with outcomes for students who are forced to attend their local public school whether it's the right school for them or not.
This problem is further compounded because the voucher students were coming disproportionately from magnet schools, so the comparison group already includes a lot of "school choosers." This is like testing the effectiveness of a new medicine by giving the test group a full dose of the medicine and giving the control group a half dose. That's just not scientific.
As it happens, numerous studies that avoid these methodological problems find that voucher students in private schools do better. Most convincing are seven studies that compared students who won a random lottery to use a school voucher at a private school to similar students who lost the lottery and stayed in public schools. All seven found that voucher kids had better academic outcomes. Studies using other methods confirm these findings.
Let's hope this misleading research doesn't distract from the real scholarly consensus finding that school choice works.
Greg Forster is a senior fellow at the Milton and Rose D. Friedman Foundation.
