The primary reason that there should be a distinction between students with different types of disabilities or learning challenges is that one type of student could pose increased risk of harm or interfere with the learning of the other. For example, an autistic student might physically harm a fragile student with cerebral palsy, who should be taken and remain out of his/her wheelchair for determined periods each day; and a student with Attention Deficit Disorder may become distracted by autistic students who create significant disturbances during class time. And, especially if the autistic student is interactive, it can cause an uproar amongst the other students.
I worked in a class with an autistic student who would fall to the floor and spin around as though break dancing. The other students in the class thought it was hilarious. The same autistic student would bite his hand and then chase other students, endeavoring to touch them with the saliva on his hand. A considerable portion of each class day, when the students weren’t laughing while the autistic student was “breakdancing,” they would literally be running from him, while I and the other instructors grappled to maintain order.
On the flip side of the coin, there was very little time to give the autistic student the level of academic attention that he needed, noting that autistic students, even those who are incapacitated and/or cannot speak, etc. should be rendered structured academics, considering that miracles do happen, and if such students are suddenly capable of speaking, etc. they’ll likely remember what they were taught.