This issue involves social, political, racial, and even religious norms. Poverty, though is the biggest overarching factor. That said, it's hard to teach when the things you are describing are happening.
The school can't work on these issues in isolation. It needs to involve other community mental health and social service agencies. Families can't change, at least the amount of change needed here, alone. Washing their mouths out with soap might stop the behavior in the short term, but it won't solve any of the real issues. Until this country decides to really tackle inequality, well, it will continue.
I wish I had an answer, but I don't.