IIRC, these schools aren't as anarchic as say worst case scenarios you're thinking of from the DC and Baltimore metro areas.

With that said, there way more spots available in not nice schools than in nice schools districts. If you're not Catholic, you can't teach in the few Catholic schools left. So it's either charter schools, or um, you earn $50K with that BA in teaching. For most teachers, they'll ride it out for as long as possible until they vest in the pension plan, their student loans are paid off, or a better school comes along. My friends that operate buses and subways in the worst neighbourhoods are in a similar boat.