We had two fighting cockerels at age 16 weeks--bleeding neck on one, awful. They had gotten along until then though had frequent staring matches. Once the bleeding one had recovered, i.e. the next morning, we stopped their fighting by placing the one who started it into the penalty box (small run by himself, size two sq meters) for a few hours. When letting him out we watched again, and again the aggressor went to the box. Who started would change so each had had his turns. This went on for two days, and then it was over. No more fights. They avoided one another for a day or two, but then were back to being buddies.
These are Orpingtons. From an Orpington expert, I learned that Orpington cockerels establish a hierarchy among themselves and no longer fight. Also, they will not fight to the death. There was another breed, I wish I could remember which one, whose cockerels do not fight. So I don't know how this would work on other breeds, or even other Orpingtons. I don't have much experience with cockerels.
Is your cockerel attacking your children? I think, I might try the penalty box if you can be very watchful and quick about it.
We had done the penalty box thing with an aggressive hen who kept bullying one of our other hens. She learned so quickly that after two penalties, she ran to and pecked the little hen, and then immediately turned and ran straight to the penalty box without our having a chance to go after her. Needless to say, this penalty did not seem to work on her. Incidentally, while standing in the penalty box, she would noisily complain and wail away most pitifully. If that happens you need to devise something that will get the message across to your cockerel. They can learn but they do have a strong will of their own.
Another thought: you might want to observe the conditions immediately preceding the bad behaviour to get a better insight. Just realized this is a very old blog, but just in case of interest to any other readers...