What's your way of handling this? I'm trying to find the right balance with my nine year old as we move into tougher material. It was easier to take a million short breaks when he was doing little kid stuff.
We have a similar situation with our 10yo, and have yet to find a solution. My experience is that he works best when he's exhausted :-). If we've done yardwork all morning, or cleaned the church for a few hours, then he settles right down after lunch!
The best suggestion I have (other than moving to the farm!) is to skip as much busywork as possible ... if he can do the multiplication, move on to the division. Cut down the paper practice. Drill on math facts while you're in the car, or analyze sentences. Teach him to type, so he doesn't have to sit and write.
And remember God made boys the way they are, so if they're driving us (parents) insane, WE have a problem, not the boys!