I send him out to jump on his trampoline and tell him he has to keep jumping until he's ready to do school work! lol That helps cut down on the excess or frustrating behavior. If that doesn't do it. He knows we have to do so much every week. If everything that is assigned for the week isn't done, we finish on his free day. His choice to do it on a school day or his free day.
I usually write down his schedule on the dry erase board so he can see what subjects we are doing for that day. He gets a free choice which is usually using his iPad, computer, or watching a movie after he completes his lessons. I just incorporated a behavior chart. This works sometimes.
At home is one of the only places my son has ever got the more advanced academics he craves. But he tends to want to do his own thing. I offer him preferred activities as reward time for doing things I want him to do.
We like to use our Wii Sports between lessons or sometimes I just need to break the lesson up into smaller pieces.