Is it possible that different parts of USA have different situation, because of a different state, different county, or just depending on whether the parents in the specific school are politically savvy, know their rights and fight for them?

Sometimes the official rules are the same for everyone, and yet what actually happens, depends more on the local culture. Maybe the lawsuits get big media attention, but in reality they happen rarely and require a lot of effort on parents' side (or a coincidence that some political group decides to push this cause), so most parents don't even try.