Critics of the Bush administration had a field day, or two, or three a while back when the U.S. Department of Education released a long-delayed report that purported to show private schools did not outperform public schools when students’ background characteristics were taken into account. Essentially, the report’s authors concluded, higher test scores among private-school students reflect the fact that they are wealthier and healthier on average than their public-school counterparts, not because of any intrinsic advantages of private education. See, the Bush-bashers said, this dishonest administration tries to bury any unpleasant news that doesn’t comport with its ideological presuppositions. Bush lied, schoolchildren cried, or something like that.
Another possibility, however, was simply that Education officials had concerns about the methodology of the study. Now, thanks to the indefatigable education researcher Paul Peterson at Harvard University, we have reason to believe such concerns were legitimate. Looking at the same National Assessment of Educational Progress testing data that the original researchers used, Peterson discovered that they made questionable choices about how to adjust for student characteristics. The use of Title 1, a federal program aimed at disadvantaged students, as a proxy for family poverty was poor choice. It ends up overestimating low-income kids in public schools and underestimating them in private schools.
The bottom line, Peterson found, was that more-sensible adjustments for student characteristics left private schools outperforming public schools in 11 of the 12 outcomes measured. Because the results of several experimental studies — in which low-income students were randomly selected from an applicant pool to attend private schools with vouchers — also showed a clear and significant private-school advantage, Peterson’s findings are very credible. You can read more here and here.