I personally was constantly fiddling with something, be it drilling holes in erasers or doodling or whatever, but I was always doing something. Had I not been able to do something (allowed... now that's a different story ;)) I would never have passed a single subject! Just tiny tasks to keep myself busy while I was listening. Even to this day, a couple of decades later, I can't really concentrate on one task.
That said, people learn differently. Some people can just put their mind to it and grind through material, others, like me, aren't quite so fortunate. If only there was a way to gauge the learning method most suitable for a child, and put that child in an appropriate class... I believe things in education would look a lot brighter.