Wall street journal had an opinion article on Mainstreaming special education students.
http://online.wsj.com/article/SB10001424127887323309404578613532497541300.html
This was a lot of conversation at the table in our house. Anybody outside of education would be astounded by what the law is.
(this is highly, highly simplified)
There are generally two types of students who qualify, first is special education. These are students who cannot learn as fast or as well as other students. Say what we used to call "mentally retarded". Johnny can't learn as well as other students. He gets more time for tests, and limited multiple test responses (say remove "a", and on tests hard open response are removed. A person outside would think, "hey, its not the same. This student does not know as much as the other students" No, but it is the law.
The other type is 504. These are students with disabilities with learning. Sight problems, hearing problems. These are students who can learn, there is just something in the way. Let us say that Jeffrey is deaf in is right ear. I must put his seat so his left ear is toward me. Jennifer just plan has vision problems and needs large text books and tests. This can work. But what happens when Jeffrey keeps moving out of that assigned seat? I spend time getting him back into the seat. Did Jennifer fail because she cannot see the text to read it, or because she spends all her time talking with her buddies? Now, toss in ADD or ADHD which is physical... and a whole new thing has opened up.
There are others ESL, or others.
We can fail students who do not perform, I could and can document, "I did everything and your child did not perform." I know of lazy special education teachers. Many are hard working, dedicated and patient etc. One, would about every two months send an email asking how the special education students were doing in my class and I would choke down "It is on the electronic grading, look it up yourself."
"Mary," has been in special education for a long time. It was not notacible in the Elementary grades, but as her buddies moved on, she fell behind. But because she's been mainstreamed for so long nobody steps forward and says, "she needs to go to lifestyle classes." The keep going with the flow.