My 15yr old son in a bit of bother at school.?

He's about to sit his GCSE's and recently during a lesson in DT put a craft knife in his pocket and forgot to hand it in. He subsequently handed it in to a teacher but the school have now excluded him for three weeks for theft and carrying an offensive weapon. There is to be a meeting with the Board of Governors shortly when it will be decided if they let him back to school at all. I dont know what to do.