I didn't often get punched in the face when I went to school, but it for sure happened once or twice. What I discovered early on is that if you really seize the day, you tell would-be bullies that you are too vibrant for their bitterness.
Get a sweater on that child, for-crying-out-loud. Make it an amazing one. One with tassels and sequins and Santa. Make a real aggressive statement that your child 'IS HERE, he HAS NO FEAR, and he REFUSES your FACE PUNCH, good sir'. Meanwhile, the low key element is that a really sweet Ugly Sweater acts as an amazing diversionary device. You can swing it over head, go for the old neck choke, or the tie to a pole, temporary cuff. As a little person, all important survival methods.