The standards of society that the boys brought with them when they landed on the island are not the standards of society present at the end of the story. The evolution of the social relationships among the individuals and groups reflected the changing outlooks, attitudes, and actions displayed as time went by.
When the full group of boys comes together and comes to grips with the fact that there are no adults on the island, their first determination is to maintain a social structure as similar as possible to what they were familiar with at home - the English school system. Jack announces, "We've got to have rules and obey them. After all, we're not savages. We're English, and the English are best at everything." Rules for conduct and hygiene are determined and agreed upon.
With time, the rules go unobeyed. Ralph fights to maintain the structure of home, but things move out of his control, as he realizes when he says, "Things are moving breaking up. I don't understand why." Ralph's primary opponent in the struggle for leadership, Jack, demands and obtains the attention of the group, even though he doesn't have the conch.
In a moment the platform was full of arguing, gesticulating shadows. To Ralph, seated, this seemed the breaking up of sanity. Fear, beasts, no general agreement that the fire was all-important.
As the question becomes "Which is better - to have laws and agree, or to hunt and kill?," the decline into a society based on the most basic of animal instincts is confirmed.