what is the moral lesson of the story
I agree with the answer above but would like to point out the historical context of the book, an understanding of which, I believe contributes to the understanding of the message or theme of the book. Golding wrote this book shortly after World War II when Europe, which had considered herself "civilized" for generations, was the setting of some of the most horrific atrocities in the history of the world. I believe that part of the lesson or insight he wants to give us in the book, is that we cannot be complacent in our "civilization" We might be wealthy, educated, generous, peaceful in our ordered world, but once that order is disrupted, we can go back to the bestial nature that we naturally have. Our inherent weakness cannot be solved by "civilization."