You're only assuming or guessing. You really have no way of knowing what the 'vast majority' of them are, or aren't.
All we have in this discussion are our own subjective opinions. I look around and see that the vast majority of Americans (the majority of whom went to public school) are decent, fairly religious, productive members of society. They have, for example, one of the highest per capita charitable donation rates in the world.
You, on the other hand, have a few sensational stories about what goes on in public schools that serve to reinforce your predjudices against public education.