Diana Jean Schemo, New York Times:

A large-scale government-financed study has concluded that when it comes to math, students in regular public schools do as well as or significantly better than comparable students in private schools. …

… Though private school students have long scored higher on the national assessment, commonly referred to as “the nation’s report card,” the new study used advanced statistical techniques to adjust for the effects of income, school and home circumstances. The researchers said they compared math scores, not reading ones, because math was considered a clearer measure of a school’s overall effectiveness.

The study found that while the raw scores of fourth graders in Roman Catholic schools, for example, were 14.3 points higher than those in public schools, when adjustments were made for student backgrounds, those in Catholic schools scored 3.4 points lower than those in public schools. A spokeswoman for the National Catholic Education Association did not respond to requests for comment.

Now, for how many years has conventional wisdom been telling us that private schools are better than public schools? That the way to “save” public education was to give kids vouchers to pay for private schools? That parochial schools in particular were better because they could educate kids with lower per-pupil costs?

That last part always was a howler, because parochial schools generally don’t provide special education, and public ones must, and special ed programs are expensive. (Years ago I worked with a woman who had sent her children to Catholic schools, and only after her daughter had graduated high school did she learn that public schools would have worked with the girl to correct her speech impediment. Catholic schools didn’t bother. Boy, was she mad.) Also, parochial schools can bounce kids with behavioral problems, and as a rule public schools can’t until the little darlings get sentenced to juvenile detention.

Kevin Drum writes,

The study analyzed only the math portion of the NAEP test, and the results from the 4th grade test are shown below. The red line shows the average public school score, and the raw scores for most types of private schools (the black bars on the graph) are higher than the public school average. However, much of this difference is due to the fact that private schools attract better kids in the first place, not because the schools themselves are better.

So what would happen if both types of schools had similar student bodies? Those results are shown for private schools in the gray bars in the graph, where test scores are controlled for demographics, and they’re considerably lower than the public school average. In other words, if you took two similar kids and sent one to a public school and one to a private school, the kid in the private school would probably do a little worse than his public school twin. (Note that a difference of 10 points is roughly equal to one grade level.)

The 8th grade results are better, with most private schools scoring about the same as public schools. The only exception is the conservative Christian schools, which continue to score considerably lower than public schools — although the sample size is small enough that the results aren’t conclusive.

Worth bookmarking, I say.