Lord of the Flies demonstrates the violence of human nature, and how lack of controlling influences can result in bringing out that violence.
Although we never really see the boys before they are on the island, we can assume they were generally normal boys. Jack’s choir arguably the most violent boys, are actually the most obedient in the beginning. They remain obedient, but follow a violent leader and therefore become violent.
The creature was a party of boys, marching approximately in step in two parallel lines and dressed in strangely eccentric clothing. … The boy who controlled them was dressed in the same way though his cap badge was golden. (ch 1)
It is no accident that the word “controlled” is used. Jack continues to control the choir throughout the book, and from the beginning they are seen as one group, and Jack’s domain. The choir becomes the hunters, and they eventually make up the base of Jack’s heathen tribe. If any of them disagree, they have lost their identity to the point of not being able to contradict Jack.
Above all, this book is an exploration of human nature. We humans are followers. We are more than willing to give up our identity and morals to feel like we belong, and in the mob mentality what the group does becomes more important than what we think.