A legitimate mental disability often viewed as a made up excuse for poor performance in school (which it frequently is.) It is natural for children to display signs of ADD, this does not however mean they are afflicted. It means they are normal, well-balanced human beings. Symptoms generally fade in the early teens; if by 15 an individual's condition persists or worsens, they may (but not always) be justly diagnosed. However, for those who genuinely suffer, the clarity of mind the medication can provide is priceless and worth irritating fakers who discredit the illness.
This is not a sign of stupidity; in fact, ADD frequently affects those with above average IQ's, such as Ivy League students, and many renowned geniuses throughout history. Though the occasional genuine moron and/or average thinker will fall victim.
A test of whether or not the condition is actual could be if the individual in question has difficulty focusing on the activities they enjoy as well as activities they dislike.
While his fellow students have learned to concentrate on assignments, Alex remains unable to focus on the simplest task.