I'm with RockRose. I have worked in school districts a long time and have never heard of a compression band so really don't know how to respond. So am very curious as to what it is.
In regards to him dropping his pants. If that was his first time doing that I probably would not have suspended him. But things are much tighter now. You get one girl seeing that and complaining to her parent and the police are involved. So it was certainly justified action by the principal (but perhaps not called for).
What you definitely need to be doing is trying to get an IEP or a 504 plan going to protect him. If you are not sure what that is - get "The ADD/ ADHD Answer book," by Susan Ashley. There is a lot there that will help you, his parents, and him.
What is a compression band? The only ones I know are for injuries - if you have a hernia, or an injured knee, etc., or an injured wrist, compression bands help hold the injured part in place to reduce further injury and pain.