I dont think add/adhd is a learning disorder?
Now their is still debate if its a real disorder at all but lets just ignore that for now. Its classified as a learning disability. However I not sure it should be. I will present why. ADD/ADHD is hyperactive(ADHD) and a lack of of attention skills(ADD/ADHD).
Now hyperactivity and issues paying attention can be caused by a number of things. Stir crazy is what happens when a person is not let out enough and confined to one area for too long. Children have a lot of energy since they are young. Meaning if they dont have enough of an outlet they might become very hyper.
If a person does not pay attention it can mean they either don't understand the material how its taught or cant read the material as its written. It can also mean they are OCD and so are distracted by other things they believed were wrong and needed to be fixed. OCD actually has a lot of the same symptoms as OCD as well. OCD is also sometimes misdiagnosed as ADD/ADHD.
Reading skills can be caused by things like Dyslexia which might appear that they simply don't care to pay attention. However its due to the fact they cant read since their brain does not process the information normally. Their is a other learning issues that cause lack of attention skills. So I think ADHD/ADD is more a result not the actual learning problem itself.