After teaching at OU Medical School, which does turn out excellent physicians, with very little thanks to me, what I noticed was: Smart kids rise to the top, no matter what school they go to. Some of my best students were from places like Poteau and Gage (making those up, but you get my point). Private schools give you polish, but I'm not really sure it makes that much difference how well you can learn new material. What private schools may have the biggest effect on is average students, because private schools (especially Casady) tend to have more children of smart parents, which means genetically they tend to be smarter. Some average kids at private schools start thinking they are dumb or inadequate. Others push themselves farther than they would have in a public school, and that percentage of the population probably benefits from a private school education.