We've been dealing with this as well. At home, my son is used to the environment and everything is structured/set up in a way that he's comfortable with; however, at school, things can get crazy, which can lead to meltdowns when a child is overwhelmed by all the stimulation. After having to pick him up early from school several times in a two-week period, I had a conference with the teacher to get to the root of the problem. Turns out that because it was the last month of school and testing was complete, there was no routine. He NEEDS routine -- or at least he needs to know what to expect!
Anyway, we made picture schedule with velcro-attached activities, allowing the schedule to be customized everyday. There are also fun choice/break/help cards attached in his "work" folder (we use this for classwork and homework -- it basically lists tasks in order and has all independent work paper-clipped inside), so his rewards are also visual and he feels more in control. Also, to cut down on distractions, my son has earplugs, sunglasses, a quiet space, etc. available for when he needs them. We're also trying to get lamp lighting in his classroom, which I have found while teaching Sunday school helps keep things calmer (besides, flourescent lights are irritating in a number of ways).
Hope this helps, and if anyone else has any creative suggestions, I'd love to hear them!
