A 2017 study in the District of Columbia about the effects of private school vouchers has further confirmed the results of recent studies in Indiana, Louisiana and Ohio. By and large, the performance of voucher students on standardized tests who transferred to private schools has declined.

Three studies since 2015 were much more rigorous than previous ones, some of which showed modest improvement or no net gain positive or negative. The samples were not randomized nor were the results compared to public school students. Overall, most of the research methods were found to be flawed.

When Vice President Mike Pence was governor of Indiana, he extended the state’s voucher program, which now costs $153 million and serves 35,000 students. Researchers found that among these students there was no improvement in reading, and in mathematics there were “significant losses in achievement.” Private voucher students with disabilities did especially poorly.

In Louisiana many vouchers are assigned by lottery, which has given researchers the advantage of a randomized sample. This is key to successful statistical studies. The most recent result was that “the scores of the lottery winners dropped precipitously in their first year of attending private school, compared to the performance of the lottery losers [still in public schools].”

Reading scores for Louisiana’s voucher students also declined, but the most dramatic change was in math: the average lottery loser remained in the 50th percentile, while the winners dropped to 26th in a single year. After three years the math scores did rebound to the 34th percentile.

Harvard education professor Martin West states that the negative effects in Louisiana were “as large as any I’ve seen in the literature, not just compared with other voucher studies, but in the history of American education research.”

A previous Louisiana study with a small sample size showed a drop in math performance for two years, but then a return to the level of public school test results. The 2015 study increased the number of students and the low scores continued after three years. This result is obviously the one to honor.

Critics might respond by saying that this research is being done by “liberal” professors. However, a study done on Ohio students by the conservative, pro-voucher Thomas B. Fordham Institute was released in June 2016. The conclusion was consistent with other research: “Students who use vouchers to attend private schools have fared worse academically compared to their closely matched peers attending public schools.” Once again, results were worse in math.

The voucher program in the District of Columbia was the first program to use federal funds ($60 million to date), and its lottery basis allowed for randomized data collection. Researchers from the Department of Education found that math scores for voucher students were significantly lower than lottery losers who stayed in the public schools. Reading scores were also lower for voucher students from kindergarten to fifth grade.

The Republican response to this study was to ban randomize data collection by the Department of Education and to mandate a return to the less rigorous methods of previous studies that showed modest progress among voucher students. The good news, however, is that this same bipartisan budget bill did not include $1 billion in federal funds for vouchers that President Trump had requested.

Voucher proponents contend that parental satisfaction and graduation rates are better measures than standardized tests. This is curiously ironic because these same people used the latter to argue that test scores proved that public schools were failing. Although flawed and overused, standardized tests are the only objective measure of student success.

Parental satisfaction is an especially weak criterion of assessing quality of education. Some conservative Christian parents might be pleased to learn that their children’s textbooks teach that “the Jews plotted to kill Jesus,” that evolution is an atheistic invention, or that climate change is a hoax.

These unregulated religious schools are not what free marketeer Milton Friedman had in mind when he started the school choice movement in 1955. Friedman required that vouchers were to be used for “approved educational services” at schools that “met certain minimum standards.” The only standard for many of these schools is the Bible.

Under intense pressure to improve test scores, our public schools have reached the point where their performance is the same as or sometimes better than private school achievement. This fact, plus the negative results of using taxpayer money for private schools tuition, proves that the parental choice movement no longer has a leg to stand on.