J.W.
Are you sure that is what he wants. When I graduated I didn't want my kids doing anything but eating a fancy meal with me. Sure I was running around with a pencil casting spells on people but more than anything I wanted it to be a mature moment. Kids with sayings on their shirts would not have fit in.
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Oh, if you don't get the spell reference, the only thing that makes you look more like a Hogwarts cast out than the master's robes are that of the PHD! Strangely most of the professors claimed to be Slytherin. :p