The other thing to consider is Jack's role back in his "real" society. Knowing that Jack is an aggressive, authoratative kid, we can assume that he was probably reprimanded in his prior school. Since he was probably in attendance at a preppy private school, we can also assume that his reprimands were probably harsh. Now, because of the crash and getting stranded, Jack's in a position where he can carry the power. This would have been almost a dream come true for him. Any anger he has built up from his own prior punishments could now be expended on these other boys.
One of the many questions that has plagued political thinkers is the question of the legitimacy of power. In most societies, some people power over others. Some issue commands that others are expected to obey. The question arises as to what constitute their authority, and here there are many answers. Jack then, is authoritarian man. Like Hitler and Mussolini, he came out of an authoritarian tradition; himself a Satanic figure with his red hair and black cape, he was also the leader of a black-capped and black-cloaked gang that marched in step something dark [that] was fumbling along and followed orders. His was the voice of one who knew his own mind, and when it was suggested that there ought to be a chief he immediately and arrogantly demanded that position for himself. Defeated in an election, he took command of the hunters, the forces of naked power. We'll have rules! he cried excitedly. Lots of rules! Then when anyone breaks 'em .” He creates rules in order to have power over people—rules legitimate his power and gives him reason to exercise it in cruel ways.
Jack is very enthusiastic about creating rules for others because it gives him power and makes him feel like he is important.