It's both. Certainly there are those who legitimately suffer from the condition, as you put it, but there a greater amount of young boys who are misdiagnosed by teachers with no legitimate experience over the ability to diagnose besides: "he's a distraction to my classroom".

This characterizes Zimbardos more recent work on "The Demise of Guys" where you can learn an overview about it here[0]

The great issue is the vast amount of boys being misattribute with the condition, from predominately female teachers.

I was one of those boys, but I was one of the few lucky ones who's father is a doctor and never had me prescribed medicine I didn't need. I ended up excelling in upper school.

[0] http://www.ted.com/talks/zimchallenge?language=en