the data is very very old (20 years), but they did not find significant differences after adjusting for the schools / students characteristics. Unadjusted scores however do look better for private schools.
thanks, but I think that comparison is not fair, if you're throwing all demographics in one bucket. E.g. I'd bet income explains most of those differences.
I'm on the fence about public schools in the US as I'm originally from a different country where private schools are a rarity, but I've learned how bad schools can be here. Anecdotally here in NC public schools have a much better reputation than private.
I would reference the confirming NAIS studies as well but they've got some self-interest in those results.