Many children profit from sitting on a disc-o-seat when they do homework or even when they are at the supper table. Problem is, they are inordinately expensive (Try $43 with shipping). I have found the FITball at a medical supply house that works just as well.
FitBALL Seating Disc, 13” for $20.74, now on sale. The 15” ones are $24.20, and are more a propos for Grades 3-4.
Have a Seat!