Judging by the way he inches closer and closer to the bar before going up for the header, there's a good chance this kid was trying to do this on purpose. Still, jumping up and slamming your head into a metal bar looks painful. And there's a good chance that blow knocked the ability to read out of his head.
UPDATE: OK, so maybe the kid just hits the bar with his hands or his hands and his head. Either way, that other kid's laugh is annoying.