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.

This goes back to the parents who aren't taking their child to doctors for health checkups for any myriad of reasons. Early and often checkups should catch these issues. In your example I wouldn't say parents don't give a shit. But as someone who had ADHD but didn't cut up in school or wasn't a class clown, I had discipline at home. Sure I would talk during class and my mind would wander. But I wasn't being so disruptive class couldn't be taught.

Almost always in the examples of why teachers don't want to teach anymore. The focus is always on pay, testing, and administration. But who wants to come to work and teach children that are so disrespectful and so disruptive that class can't be taught. My salary wouldn't be the deciding factor here.

As a parent, you can be well very well informed on the issue, and still not be able to solve it in your kid. I'd venture that this kind of futility is more prevalent than ignorance.