I had a head banger once in centre care and it was horrible to see if I didn't get there in time! Mostly we would shadow and redirect before he would throw himself down but if a full out tantrum ensued we would swiftly pick him up and put him in a high chair and coach him to take deep breaths. When he was calm we would say things like "Miss Lou doesn't want any of her friends to get hurt, and banging ____'s head on the floor hurts ______. When we get angry we take deep breaths. All done hurting _____'s head."