I read and studied this in school. I didn't much like the writing style, but the Golding does effectively create the atmosphere he wants.
The progressive breakdown of goodwill and friendliness among the boys marooned on a desert island is usually taken to suggest that humans are essentially base, authoritarian creatures that will behave cruelly and selfishly, the strong lording over the weak, without strong rules, a stable system of ethics & truth (a memorable scene in which a fire distorts the appearance of faces is used to suggest the deadly danger of nihilism and uncertainty) and the restraining influence of strong rational leadership and deeply instilled tradition. I reject that hypothesis, which is one of the foundations of the imperialist ideology that constructs 'savages' 'barbarians' as inferior to their 'civilised' colonisers.
This book is a story of conflict between the supposed 'savage' instinct and the 'civilised' instinct for mutual protection and justice, the latter losing the battle. Evidently many 'savage' societies everywhere live in peace and harmony with far more egalitarian principles and markedly less violence than within and between 'civilised' nation states. While I believe (based on experience and studies!) that most children and young people have a strong sense and desire for justice and fairness and think Golding's account is really unrealistic; if I were presented with it as a true story, I would blame the violent disintegration on the pernicious influence of socialisation in a kyriarchal culture rather than 'natural' tendencies.