When I was a kid, my dad played with me prior to doing homework. We burned up some of my energy and I could focus better. He would always choose an activity that used my senses. One of his favorite games with me was to throw a tennis ball on the roof and I had to catch it as it fell from the roof. When I got older, about 8 to 10 years old, he would try to shove me away from the ball so it would be harder to catch the ball. It worked I my ability to focus and added a bit of heavy work, too. It was a fun activity and it allowed better concentration.

Anyway, maybe a bit of excercise using various sensory systems prior to school work would help?