I do think that the special ed model is completely broken. I think public schools overspend on special ed, and a lot of that funding is about getting special ed kids into the same classrooms as other kids and reducing the disruptions that they cause.
Instead, all students would be better served (and served more efficiently) if schools would admit that people learn at different rates, and segregated the children based on that. The disruptive special ed kids, who are often years behind, should have very small classes with other kids of the same level and lots of attention from teachers. Conversely, the kids who are good at math or reading should be put in accelerated classes.
Unfortunately, this kind of separation makes parents unhappy: they want their kids to all be in the "super special" classes despite the fact that on average, their kids are average. Parents are the ones who vote for school board, so school boards are unlikely to do anything that makes parents unhappy.
I think you are assuming special ed kids are academically slower and I have to push back on that. Special Ed encompasses students of all types. Some are mentally handicap, some have physical disabilities. One of my friends was wheelchair bound and had to leave class 5 minutes before the bell in order not to get stuck in the hallway. Others have respiratory issues that require classrooms with special equipment, special buses, etc. And then you have the deaf and blind students, hardly slower than anyone else, but they still require additional help that has nothing to do with being disruptive. Most of them weren't disruptive, just students trying to get a solid education like everyone else, and as guaranteed by the Supreme Court.
My understanding is that special ed money is distributed according to a power law: most kids classified as "special ed" actually need very little help (and very little money), and don't disrupt things for other students. I had a friend in my middle school Latin classes who was blind, and while he needed special written materials and some private tutoring, he didn't need any other help. The same is true of people with dyslexia, people who are wheelchair-bound, etc. They need some accommodations, but they are not where most of the money is spent.
Conversely, the kids who do need tons of resources are usually kids with severe mental or developmental disabilities. These kids usually have a 1:1 aide telling them what to do and trying to help them either understand the lesson or work through a totally different lesson (which also must be a humiliating experience - I would never want that for my child). I have seen both of these cases in public schools. These kids would certainly be better served by having a teacher who can pay attention to their needs instead of a teacher who can't and an aide who tries to keep up.
Instead, all students would be better served (and served more efficiently) if schools would admit that people learn at different rates, and segregated the children based on that. The disruptive special ed kids, who are often years behind, should have very small classes with other kids of the same level and lots of attention from teachers. Conversely, the kids who are good at math or reading should be put in accelerated classes.
Unfortunately, this kind of separation makes parents unhappy: they want their kids to all be in the "super special" classes despite the fact that on average, their kids are average. Parents are the ones who vote for school board, so school boards are unlikely to do anything that makes parents unhappy.