The problem is the testing.
If you have a fundamental understanding of ADD, you can figure out how to answer a questionnaire to obtain the diagnosis. I use more complex testing so that the youth especially would not be able to manipulate the document.
You probably don't actually have ADD, or you'd realize a revelation on the medication. For those patients whose pathology blocks their ability to read, calculate, organize thoughts and tasks, and solve complex problems the medication represents the key that unlocks doors to success that had otherwise been closed. Then the self esteem that follows allows a student to set their goals high and believe that they can achieve anything, as opposed to thinking that they just weren't smart enough.
The irregular levrels of naturally occurring endogenous adrenergics that characterize ADD/ADHD may normalize into adulthood, but some don't. I have dozens of patients in my practice of all ages, some in their sixties. They do not experience the tolerance that you describe over several years; that's likely to only be significant in non-ADD users.