Because Lord of the Flies was a documentary. Children are monsters. Once they decide one is weak they torment them. Even “good” kids, because if they don’t go along with the masses they’re next.
True. It doesn't matter where the children are educated, or whether their families are rich or poor, or anything else.
Public schools, private or parochial schools, homeschool groups - no matter where, some children are sweet, some are mean, some are a mixture, and they all must learn right from wrong.
It's up to the adults to guide them in the right direction and keep them under control.