The sad fact in life is bad parents create bad children. There are a multitude of ways of being a bad parent. Most commonly bad kids are created by neglectful and stupid parents. Poor people often make bad parents due to their inability stop using drugs. Rich people often make bad parents do to spoiling their child and shielding them from the real world. Bad children come from these parents.
An overwhelming amount of badly behaved children do come from bad or malfunctioning homes, however, that does not mean that all bad children come from bad homes. First of all, judging what a bad child or bad home is, is extremely subjective. Children, unaware of alternatives, tend to make the best of what they are offered in life.