School vouchers don’t just violate the principle of the separation of church and state, they pose a grave threat to public education – the system that educates 90 percent of America’s school-aged children.

As the nation marks Public Schools Week, it’s important to understand why vouchers are wrong for America, especially now with plans being pushed by the Trump-Pence administration and Education Secretary Betsy DeVos. Trump, Pence and DeVos may be big fans of vouchers, but the facts show why they’re bad public policy.

Voucher advocates rely on a number of fallacious arguments. Here are six of the most common ones debunked:

Vouchers promote “school choice.” They do in a sense – but chiefly for the people who own and operate private schools. Vouchers offer no real choice to parents because private schools routinely deny admission or expel students who fail to meet certain criteria. Young people have been rejected by private schools because they are the “wrong” religion, because their parents are deemed to have an “immoral” lifestyle, because they declined to take part in mandatory religious activities and for other reasons. The fact is, a stack of vouchers a mile high won’t get a child into a private school that does not want her.

Vouchers boost academic performance. Voucher programs have been in operation in some states since the 1990s. Researchers have had plenty of time to study them, and one thing is clear: Vouchers don’t increase student academic performance. Recent studies of the Louisiana, Indiana, Ohio, and the District of Columbia voucher programs have revealed that students who used vouchers actually perform worse academically than their peers. In addition, studies of long-standing voucher programs in Milwaukee and Cleveland found that students offered vouchers showed no improvement in reading or math over those not in the program.

People who send their children to private schools are taxed twice, once to pay for public schools and once for the private school tuition they pay. Private school tuition is not a tax; it’s an extra expense some people have chosen to bear. You don’t get a tax break because you’ve chosen to patronize a private provider for a service the government makes available. If that were the case, people could demand tax breaks because they buy books from Amazon and don't use the public library, because they built their own swimming pool and don’t go to the municipal one or because they own a car and don’t rely on mass transit. There are certain public services we are all expected to support, even if we don’t use them directly. An educated citizenry benefits us all. That’s why most of us pay taxes to support public schools, including people who don’t have children and people whose children are no longer in school.

Vouchers spur public schools to improve by introducing an element of competition. The public school system and private schools are so dissimilar that there can be no true competition between them. Public schools by law must serve all young people. Private schools can select certain pupils and turn away others. Public schools are answerable to democratically elected boards. Private schools are free from most forms of state oversight. In addition, voucher plans siphon tax money away from public schools. It’s difficult to understand how giving public schools less money somehow makes them more able to “compete.”

Private schools offer a better education than public schools. This assumption is taken as a given by many Americans, even some public school advocates. But there’s little data to back it up. In fact, a 2018 study by researchers at the University of Virginia found the advantages private school students have are due to family income and education levels, not the private school. The UVA researchers noted, “In short, despite the frequent and pronounced arguments in favor of the use of vouchers or other mechanisms to support enrollment in private schools as a solution for vulnerable children and families attending local or neighborhood schools, the present study found no evidence that private schools, net of family background (particularly income), are more effective for promoting student success.” Other studies have found similar results.

Furthermore, not all private schools are well-funded academies, and many are of poor quality. Some schools run by religious groups teach certain subjects with sectarian bias. Schools run by fundamentalist Christians, for example, often teach creationism in lieu of evolution and offer a fallacious “Christian nation” version of American history. Students who attend these schools can emerge at a disadvantage in certain subjects.

The American people support vouchers. No, they don’t. Polls have consistently shown that a majority of Americans opposes voucher plans. And the more people know about vouchers, the less they like them. This probably explains why vouchers and other private school aid plans have been decisively defeated in numerous ballot referenda since 1967.

To learn more about the threat vouchers pose to public education, visit the website of the National Coalition for Public Education.