My very active sons are 9, 7, and 4. It has helped tremendously to have a routine/schedule for our schoolwork. They know what's expected and they know what's coming next. We will usually do about 30 mins of one-on-one time per subject, then whomever I was schooling gets a break while I work with the other one for 30 mins, or so.
Hope you come up with something that works well for you!