This essay originally appeared in USA Today. 

Political leaders are asking the nation to double down on the bet that expanding school vouchers will improve educational outcomes. Arizona — ground zero in the Koch network's efforts to reshape education — is set to decide a voucher referendum this fall. A dozen other state legislatures have passed or are considering their own voucher expansions. And the Trump administration is cheering them on. It created a private school loophole in last year’s tax reform and is now asking Congress for new money to expand school choice further. 

These pushes rest on a false premise — that there is a private school advantage.

Private schools’ higher average test scores drive this myth. The problem is that average test scores alone do not tell us anything worth knowing. Comparing the average scores of private and public schools is comparing apples to oranges. Public and private schools enroll students from very different backgrounds. Most important, more than half of public school students are low-income. Only about one in four private school students is low-income.

Private schools don't add value

These numbers are all but destiny for a school’s overall achievement. Low-income students face a number of personal obstacles that depress their performance — from housing instability and hunger to a lack of academic support outside school. These challenges follow low-income children no matter what school they attend. An overall school’s achievement, then, is largely dictated by the percentage of low- and middle-income students it enrolls, not whether it is public or private. But simply enrolling a larger percentage of middle-income students doesn’t mean that one school is better than another.

The question to ask is whether the average poor student performs better in private school than in public school. That is what we call “value-added” and something worthy of public investment. But the data say there is not any value-added in private school.

University of Virginia researchers recently followed a cohort of children from birth to age 15, as they moved in and out of private and public schools. Once they compared apples to apples — “simply controlling for the sociodemographic characteristics” — the so-called private school advantage disappeared. They could not find any “evidence to suggest that low-income children or children enrolled in urban schools benefited more from private school enrollment.” 

Another team of researchers examined every public and private school in the nation. They found that after controlling for demographics, public schools actually slightly outperform private schools.

Federal and state leaders either have their heads in the sand or are trying to dupe the public. They have been pushing for more vouchers for private schools and slamming public schools for the past decade. Over that time, 29 states have significantly reduced public education spending — some by as much as 37 percent. Yet, during this same period, states like Florida and Indiana substantially increased the amount they would spend per voucher and quadrupled the size of their programs.

At the federal level, Education Secretary Betsy DeVos says the public school model is flawed and wants to radically expand charters and vouchers. The president’s proposed 2019 budget would cut or eliminate several public school programs, including a grant program for teachers. It would use that money for $1 billion in new grants for private and public school choice programs.

Public school funding makes a difference

The trouble is that public school funding levels actually matter a lot in how students perform. Examining decades of national data, a recent study found that a 20 percent increase in public school funding corresponds with low-income students completing nearly a year of additional education — enough to drastically reduce achievement gaps and adulthood poverty.

A follow-up study focused on the past decade of funding cuts and found that they depressed student achievement.

Spending money on vouchers rather than public schools is not based on facts or good faith efforts to improve outcomes for needy students. It is an ideological position about the role of government. The new pejorative term “government schools” and the fact that voucher programs are increasingly directed at middle-income students show that the current push isn’t about honest reform.

People send their kids to private school for a variety of reasons that make sense for them as individuals — religion, status, unique opportunities and personal flexibility. But when it comes to public policy, government can do nothing better right now for students than to fully fund public schools.