In Chapter Two, the boys are discussing rules to have on the island. They discuss splitting up the choir to have certain groups to keep the fire going and certain groups to hunt (and protect themselves from the alleged "beastie"). Seizing an opportunity to assert himself as a leader, Jack agrees that rules are necessary:
I agree with Ralph. 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. So we've got to do the right things.
Jack says this near the end of Chapter Two. Jack takes advantage of any opportunity to obtain power and here, we see his personal and national pride.
William Golding, the author, is British (English) so his audience would likely have assumed the boys were British. Lord of the Flies was published in 1954 and Golding's service in WWII (1939-45) included participation at the D-Day invasion in France. Note that Jack said "we're not savages" and yet that is what many of them become. Even if we consider that England was on the righteous side in WWII, it does imply that, sadly, anyone is capable of savage acts: in the real world or in the allegorical world of the novel.