The colleges around here its called "auditing" a course. Not sure why.
At least at one of the colleges its dirt cheap but you can't sign up for it until after all the paying students have registered.
IEP, yep, that's the main of it. Its mandated by US federal law. Its is developed by a "team" for students. The team must include a parent or gardenant, a mainstream teacher, and a school admin. The team must consider, but do not have to implement, any suggestions made by outside evaluators. As a practial matter though, the school would be hard pressed to justify NOT implementing the suggestions.
I have a love/hate relationship with IEP teams....
BeeBee