I have taught art to several special ed classes. They have won numerous prizes in competition against regular ed classes and consistently win first in all catagories and grade level they enter. Art is a common denominator, and builds self esteem, teaches concentration, sequencing, procedures, systems, job skills, and all sorts of disciplines.
It is too simple just to say it isn't any different than other students. Most have not had any exposure to art, their entire world has been in front of a television, and they begin by saying, "I can't", "do it for me", and lots of other excuses.