Another thought: in a general classroom, the average severe ADHD child will receive 20,000 additional corrections in their school years. They are also more susceptible to bullying or misunderstanding with teachers and peers. A viable solution would be a classroom specifically for students like this in which they could spend years learning in a method which works for their brains, being taught self-regulation skills and interacting on a more limited basis with the general population until upper elementary at the earliest.
We see self contained in our minds as psych wards because they were never categorized by disorder. If we had specialists working directly with specific disorders, we could see students learning on a level which is more supportive to their success.