I think the answer to this is that schooling/care for people with disabilities that make it impossible for them to succeed in normal school should be a totally different budget with different success criteria than the budget for normal school.
There are two different and contradictory goals here- the current dynamic where every gain for one is a loss for the other creates a ton of bad outcomes across the board.
In my experience ( to be fair which was a while ago ) things like that just end up making things worse trapping people and leading to a lot of lashing out
Honestly education really feels overthought and micromanaged already the whole setup is unhealthy
You are assuming that there should be distinct "schooling/care for people with disabilities" and "normal school", rather than integration, and further assuming that public schools should be competing with each other to defend and increase their budget, rather than cooperating.
What sad place do you come from?
"people with disabilities that make it impossible for them to succeed in normal school" is not a clearly divisible population from the regular student population though. Many (but not all) districts deal with disabilities via IEPs, or Individual Education Plans. They are tailored to particular students, and can be fairly common. They make things less of a clear binary than 2 separate school systems would really need.
It's worse because there's been a trend among elite districts to push students to (fraudulently) get a diagnosed disability, so that they can get accommodations on tests and raise their chances to be admitted to an elite university. So, a proposal to partition the school system into a lesser system for students with disabilities would face pushback by the aforementioned elite district parents. While they are participating in a fraud (and so it would perhaps be morally fine for them to face repercussions for it), I imagine it would make implementing any such plan very difficult.