Oh, how wrong you are.
I am very familiar with Catholic schools and their pupils having lived in Chicago for forty years where most of the white students go to these schools. The very best of them Gordon and St. Ignatius are excellent but not as good as the top public schools here: Payton, Lane, or Young. And I have met and known dozens of the formers' students and am singularly unimpressed with their overall abilities and knowledge.
Now they do play excellent football. Of course, they spend three times as much on those programs as the public schools.
My sons attended both public and private schools so I have no particular axe to grind for the p.s. just want some accuracy.