Math Is Hard said:
There should be something more to it than the opinion of a possibly overwhelmed public school teacher who doesn't have time for the more enthusiatic and inquisitive students.
One key diagnostic criterion that should be considered is that the problem is NOT situational. If a kid ONLY has trouble sitting still/paying attention in class, but can focus on tasks at home, or during afterschool activities, it is more likely they are just plain bored with school and not that they have ADD or ADHD. If a kid seems "scatter-brained" about everything they do, flitting from one task to another, never completing things, never staying focused long, then there is a better justification for further consideration of ADD or ADHD (among other things that should be ruled out) as a diagnosis.
Others have pointed it out, and it bears emphasizing that MISdiagnosis doesn't mean the disorder isn't real and doesn't exist in other people. The more I think about it, I really don't like the term OVER-diagnosis, because who sets the quota on how many diagnoses are allowed to be real before we decide it's all a "bunch of bull" as the OP put it? It simply could be that more kids are diagnosed because more physicians are aware there is a name for this behavior and there is a treatment for it too.
I do suspect there are a lot of misdiagnosed kids out there because people have NOT taken the time to fully evaluate their symptoms, the context of their symptoms, and to rule out other explanations for them. Your average general practitioner is NOT a specialist in pediatric psychiatry, and should not be the one making the final diagnosis of such disorders, but rather should be acting as a gatekeeper, saying that a particular kid meets some general criteria that merit further evaluation by a specialist. It is quite possible that normal, active, creative children are being MISdiagnosed because parents and teachers are pushing to have their lives made easier rather than learning to raise an active, creative child, but that certainly doesn't mean there aren't really people with ADD or ADHD.
If you read the older literature (I may have cited those references in much older posts here, but don't feel like looking them all up again), the diagnostic criteria are much stricter and narrower than the commonly found "if you or your child has more than 4 of these symptoms" type checklists often used to make a diagnosis today.