Sending your kids to private school doesn't make you a bad person

Melanie Stetson Freeman | The Christian Science Monitor | Getty Images

Allison Benedikt has a provocative essay on Slate arguing that sending your kids to private school makes you a "bad person."

Her argument isn't quite as outrageous as it might seem. Benedikt says that parents sending their children to private schools are "ruining-one-of-our-nation's-most-essential-institutions-in-order-to-get-what's-best-for-your-kids." The idea is that public schools are damaged when parents choose to send their kids to private schools.

I wish I could flesh out her claims more but that's about all there is.

See for yourself:

I am not an education policy wonk: I'm just judgmental. But it seems to me that if every single parent sent every single child to public school, public schools would improve. This would not happen immediately. It could take generations. Your children and grandchildren might get mediocre educations in the meantime, but it will be worth it, for the eventual common good….

So, how would this work exactly? It's simple! Everyone needs to be invested in our public schools in order for them to get better. Not just lip-service investment, or property tax investment, but real flesh-and-blood-offspring investment. Your local school stinks but you don't send your child there? Then its badness is just something you deplore in the abstract. Your local school stinks and you do send your child there? I bet you are going to do everything within your power to make it better.

There's a bit of underpants gnoming going on here.

First step: get all the children into public schools.

Second: ???

Third: better public schools.

The reason why Benedikt doesn't do a better job explaining how her plan would work is that it wouldn't. Benedikt's premise that creating a public school monopoly would improve education is demonstrably wrong. Monopoly education would, like every monopoly known in the history of humanity, produce a poorer quality product at greater cost. Competition improves education.

This isn't something that's even slightly controversial. The basic facts have been known for at least 20 years. In 1994, Harvard economist Caroline Minter Hoxby published the first empirical study looking into the effects of private competition on public schools. She found that public schools improved in almost every imaginable way. Graduation rates improve. Educational attainment rises. The post-graduation wages of public school students increases. Even teacher salaries rise when the public schools compete with private schools. What's more, these improvements didn't result from any significant increases in spending, which means public schools get these benefits more or less for free.

More recent studies show exactly the same thing. A 2011 study looked at the effects of a Florida program that provides tax credits to corporations that fund private school scholarships for students from low-income families. These scholarships mean that public schools have to compete for students with the private schools. The study found that test scores improved at public schools threatened by competition.

In other words, the facts are exactly the opposite of what Benedikt supposes. Private schools don't undermine public schools—they improve them. Which means that parents who choose to send their kids to private schools aren't bad people—they are performing a verifiable public good.

Full disclosure: I attended a private Catholic school until fourth grade, when I convinced my parents to let me attend our local public school.

—By CNBC's John Carney. Follow me on Twitter @Carney