We were fortunately spared this problem in preschool, I think because DS's school allowed them to use educational computer programs a few hours a day, so DS got to learn plenty of stuff at this own pace, then he could be patient through the other things because he'd gotten his "fix". It sounds like your school is not so adaptable.
You might want to check out this site as part of your reality check.
http://www.davidsongifted.org/db/Articles_id_10226.aspx It talks about ADD behavior vs. gifted behavior. Basically, you will see the pattern you are describing--as long as the drive to learn is being met, the behavior is fine. But when not fed intellectually, the child becomes restless and bored and acts out. I don't know if the school will be able to appreciate the difference, but at least you will feel saner!
