Private schools don't get bad students as input. (Score 1)

This is true to a certain extent-- but still, there are many kids who get into prep schools solely because they have a lot of money or their parents went to the school. I've never been in the public school system, right now I'm at a prep school. It doesn't make things better socially, even though there may not be the same oppotunities for physical violence and such. Other students still isolate the "freaks", "geeks", and "drama fags". In a few cases, last year, the entire hall of my dorm went up against one of the other students. That kind of thing has happened to me, too. Private schools often provide better education, better teachers, but they're just as hard, if not harder, for the rejects to deal with.

"Better input" is not necessarily the case. Some students want to do better at school, but they certainly are no better than students at public schools.