Like I have mentioned in previous post sensory overload IS VERY PAINFULL FOR THOSE WHO EXPERIENCE IT! One thing that you can do if they do experience sensory overload is to help take them out of that enviorment and let them catch their breath a little. This should be a place where they don't experience anything that overloads them.
This is also something that can be a good idea after school. I remember one of the people I worked with after school he didn't really feel like relating to people. He said he felt edgy. Sometime school can be a stressful experience and someone with aspergers needs a little time to just recover from that.