The late Democratic Sen. Daniel Patrick Moynihan quipped that everyone is entitled to his own opinion but not his own facts. Policymakers and pundits would do well to heed Moynihan's wisdom when they enter the fray over expanding school choice with charters, vouchers or tax credits.
Opponents of school choice regularly assert, as if it were proven fact, that choice does nothing to help students who get to choose and harms students who remain in traditional public schools.
These opponents are certainly entitled to their opinions hostile to school choice, but they are not entitled to claim as fact things that the evidence simply doesn't support. I am similarly entitled to say that I don't like the weather today, but I am not entitled to say that the sky is green - it just isn't.
The evidence on the effects of school choice is consistently positive. While we don't know everything there is to know and can always learn more, there is no reasonable way to read the evidence to suggest that choice harms those who get to choose or those who remain in traditional public schools.
To be sure, people can spin plausible stories about how choice might be harmful, but the evidence just doesn't support those stories.
We have eight random-assignment analyses of the effects of vouchers on the students who use them. Random-assignment is the "gold-standard" of research design, like in medical research, where students are assigned by lottery to a treatment group (receiving a voucher) or a control group (returning to public schools).
On average the two groups will be identical, so any difference in their achievement over time can be attributed, with high confidence, to the voucher rather than to any advantages or disadvantages they had at the start. All eight random-assignment analyses show positive effects for voucher recipients, seven of which are statistically significant.
Saying that vouchers harm or have no benefits for those who get them in light of this evidence is like saying that the sky is green.
But might expanded school choice harm students "left behind" in traditional public schools by depriving them of needed resources and talent?
The evidence actually supports a different plausible story: Public school student achievement increases when schools are faced with increased choice and competition, as schools have stronger incentives to use their resources effectively to retain and attract students and the revenues they generate.
There have been four studies on the effects of expanded choice and competition on public school student achievement in Florida, two in Milwaukee, and one each in Maine, Vermont, Michigan and Arizona. All of them found that student achievement goes up, not down, when choice is expanded. In fact, I am not aware of any study of voucher or charter programs in the United States that shows that student achievement in traditional public schools declines as a result of those programs.
You don't have to believe me. Listen to Clive Belfield and Henry Levin, researchers at Columbia University's Teachers College who are known for their skepticism about school choice. After reviewing more than 200 analyses, they conclude that "a sizable majority of these studies report beneficial effects of competition across all outcomes. The above evidence shows reasonably consistent evidence of a link between competition (choice) and education quality."
Of course, consistently positive research about school choice does nothing to stop politicians and pundits opposed to choice from asserting the opposite. It is as if they think that repeating their claims with ever-greater confidence makes them true. Or perhaps they think a plausible story about choice's harms is a fine rebuttal to systematic evidence. Or perhaps, to be charitable, they are simply unaware of what has been found in the preponderance of research on school choice.
Whatever the explanation, it is time that people stop repeating claims about school choice that are inconsistent with the evidence. Getting people to stop is no small feat. Matthew Ladner of the Goldwater Institute tried by offering a steak dinner to anyone who could produce two random-assignment studies showing that vouchers harm students who receive them, knowing full well that his restaurant budget was safe since all eight studies show positive effects.
Ladner's gambit, however, hasn't worked, as choice opponents feel free to continue repeating invented facts ignoring his challenge.
People who repeat bogus claims about the harms of school choice are basically "green-sky believers." If we label them as such, perhaps they can be shamed into stopping - or producing evidence to support their claims.
The writer is head of the Department of Education Reform at the University of Arkansas and author of the book Education Myths.