I'm pretty sure there's a ton of variation in the Catholic school experience. Certainly, a few are regarded as among the best schools in the US, while many others struggle to even match the local public schools, as far as educational quality. I know of at least one school that's diocese-affiliated but only loosely so, basically for marketing reasons, and does juuuuust enough to tick the boxes for that—they definitely don't do that kind of hard-sell Catholic indoctrination—and I doubt they're unique.