The Catholic school system has been hanging their hat on that old canard since before I was going to school. My younger brother was classified as Learning Disabled and St. Christopher's told my parents he wasn't welcome to return after 1st grade. Back then they just said he was hyperactive and to stop letting him have sugar. I don't think ADHD was really understood back then.

The other issue has to do with whether or not the parents place an emphasis or value education. If parents are paying to send their children to Catholic school then they obviously place some value on education.