I wish my parents had said something when I was being bullied. Even if it hadn't had much effect, I would have liked knowing they at least tried to have my back. So I'd talk to the director. If this sort of thing escalates--as if can do, when not addressed--someone could end up badly hurt. All the bully has to do is shove Ellie or Emma down onto something with corners and you could be looking at stitches or more.