Well, my brother had the same problem when he was in grade school and they dealt with it well. At my house, it used to be that we had to get all homework done before we could do anything "fun," be it video games, playing with friends, etc. My mom got him an agenda and had him write all his homework assignments in there. Then, after getting approval from the teacher, she had the teacher sign it every day. If my brother forgot the homework, it would be like he didn't get his homework done. He was not allowed to do anything fun that day. I think that is an age appropriate punishment and will make sure that he remembers his homework the next day.