My experience is the exact opposite and I have yet to see a private school where the top students out preformed the top students at a comparable public school. I have also seen more unqualified teachers in private school (example: Spanish 4 teacher that just graduated college at 23, never been in front of a classroom given 17 seniors and spends her time crying in the corner).

1) The lack of regulations in private school (no requirement for a teaching degree) leads to unqualified or under qualified teachers. If you don't check on every teacher then you cannot assume that they have a teaching degree.

2) The lack of normal social interactions with those outside of your economic group. Having fewer people to interact with in school limits your growth and can lead to crazy druggies/ burn outs. This is just my personal experience for being in private school most of my life. Of my graduating class in high school of 59 people there are maybe 5 or 6 that haven't fallen into hardcore drugs, gotten knocked up or moved out of their parents house. This was the top private school for a few hundred miles.

3) Cost. When I see a private school that is not predominantly white I will be amazed.

4) Every kid should have the opportunity to get a real education with out the religious indoctrination parents force on their kids. Telling a kid if he is bad he will burn in hell forever is sadistic and child abuse. Kids should be taught logic and reason when they are old enough they can make their own decisions.