How and when do Piggy and Simon fall in the novel "Lord of the Flies"?What does Golding mean by it?

Piggy falls slowly as the boys are more and more enamored
with Jack and his hunting party and draw away from the rules and rational approach to
trying to get rescued and running things.  Simon has been somewhat apart from either
group from the beginning and his fall is more rapid and violent as he emerges from the
woods, having found the beast to be within the boys, and is killed in a frenzy of fear
and blood lust.

Because Golding's novel was a response to
another that suggested that British boys might be above the violence and base nature
that other people succumb to, these boys fall is a statement that of course British boys
would be just as violent and as base as anyone if societal structures and norms were
removed.