Hi P.,
Boys learn by moving - no doubt about it. There may be things you can do to help him in an environment that believes moving is not a part of learning. Eliminating milk and most gluten proves to remove any issues if in fact he has hyperactivity. However, the science of the brain is very clear with all kids, but most especially boys, so make sure he is getting lots of outdoor playtime with lots of movement. Discuss with the teacher ways he can move about properly and if the play scheudule is appropriate. Boys also develop fine motor slower - don't hammer it. Unless there are more serious issues than I hear, your son will write. I did the opposite and killed myself and annoyed my son and he wrote on his own time anyway. Color, color, color, cut, cut, cut and get in the dirt or sand to write (maybe even on a little cookie tray using his finger - no a pencil). You can also used shaving cream in the bath - let him trace the letters in it and then erase it! The more prework you do the better the penmanship wiil be. Forcing the penmenship will just reinforce that he is bad at it. Incorporate any fine motor development with a game if you do it at home. Outside or inside, it has got to be fun! Check out a homeschool store online and see if you can get a kindergarden book of games. Whatever you do, have a happy, fun attitude or he will resist you. Praise him when he executes, don't make the praise about the letter formations, make it about the willingness.
Most likely, it is not being made fun and he is being ask to do something that is simply the most boring thing he can imagine. See if you can change that at home and see if you get a response.
J