Earlier quoted context omitted.
Public sector teachers make more than private sector teachers. http://nces.ed.gov/programs/digest/d09/tables/dt09_075.asp
Ever wonder why the private school teachers are content with their lower salary? Public sector teachers have to deal with all of the problematic students that private schools can remove or refuse to admit in the first place.
Problematic students exist in private schools and are often backed by serious money. I wouldn't make the generalization that behavior problems are only found in poor people.