I don't think the kind of student the author is talking about has ADHD symptoms or any sort of mental illness. I think they just have different personalities - and having a certain personality than the majority of people shouldn't be considered a mental illness or disorder. People are not all the same... at what threshold do we count difference in personalities as an issue?? As long as the person can keep functioning in society without major side effects (crime, extreme isolation, depression) the person is just "normal" even if they tend to work and act differently from the average.