In the book "The Lord of the Flies"... Is the Lord of the Flies an accurate portrayal of human nature?
History is full of examples of ordinary and apparently 'civilized' people doing terrible things under extraordinary circumstances, a doctor leading a death squad in the 1990s conflict in the Balkans for example, neighbours torching neighbours in Kenya, Rwanda and, in more recent days, India, pogroms in Germany and Poland during the Second World War and so on. Then we have experiments such as Milgram's, in which 'normal' people have been induced to perform very cruel things on their fellow human beings for no very important reason. It would appear therefore that the events of the novel are not as far-fetched as they might first appear and that such a group of boys could well turn feral and savage quite quickly if left to their own devices.
As for what the boys learn, I seem to recall that the novel ends too abruptly for this question to be answered with certainty but we are probably safe in assuming that Piggy and Ralph learn something but that the lessons for Jack and others will come later in their lives.