Jed, I presume you know that there are kids who have difficulty staying focused on one subject but don't have a problem sitting quietly. They get bored easily and their minds wander. I fall in that category. I did well in school, particularly college, but it was a daily struggle. Kind of like trying to drive drunk and not have an accident. It is possible but it takes a great deal of forced concentration.

Then there are kids who presumably have the same mental difficulties but are bouncing off the walls as well, disturbing the whole class.

I don't remember any hyperactive kids in the schools I attended 40 plus years ago. I am not saying there weren't any, but I don't remember them. Why so many now? 40 plus years ago high fructose corn syrup had yet to be invented. I wonder if the precipitous rise in hyperactivity has an environmental cause.