The No Child Left Behind law says underprivileged and minority kids should not have a larger share of teachers who are unqualified, inexperienced or teaching unfamiliar topics.
It puts the responsibility on states to figure out how to do that.
There's a solution to this, of course, but the unions would be against it. It would amount to "combat pay". The socialist teachers unions, which always want more money for all members and not just specific ones, just don't want to admit that money motivates. Money talks, b.s. walks.