On the flip side of that coin, you sometimes have the parents who do know all about their child's ADHD and how to (help their child) manage it effectively, and then you get these meddling teachers or principals who genuinely believe they know better than everyone else about how "problem children" should be dealt with (all while utterly ignoring the actual problem children, like bullies for example). They hear that a child has "a diagnosis" and it's like painting a target on that child for some screwed up teachers/principals, no matter how actually well behaved that child is in practice. Sometimes those vile people even go beyond "too far" and ruin lives with their meddling.