I'd be very interested to know which city and state you taught in, and whether you were regular faculty. But I think your approach to reasoning about this is misguided. Rather than taking your experiences in dysfunctional school and generalizing from that, you should be looking at how the top performing schools operate.
Special needs isn't just squirming kids. Despite having lackluster marks, our daughter was screened by the school system as gifted, which in my state is considered "special needs". The school brought in a cognitive psychologist to run an elaborate battery of tests, including a comprehensive neurological assessment. What they found was very specific, narrow deficit: slow processing speed. She was capable of solving complex math problems and generating sophisticated answers to open response questions, but even simple questions took her a long time to answer. So the action plan was to put her on a more challenging course load, but to give her longer time if necessary to complete tests. On top of that we paid for training with an educational psychologist who specializes in learning disabilities. Eighteen months later she no longer required any special accommodations and was near the top of her class.
In a nutshell, all that new-fangled bullshit worked. 30 years ago she'd have been tracked into an easy CP courseload based on her marks, but the school actually put the effort into finding out that what she really needed was to be tracked into honors and AP courses. And the school system manages to do this while spending about the national average per student -- $11,505.