In the book Lord of the Flies, where do all the boys come from and how is it that they state they are "going home" when they were leaving due to...

Although the story is told by a third person omniscient narrator, most of it is focused on what the boys directly observe on the island (the dead paratrooper and the naval officer at the end being the exceptions). The only clues we get to the boys' pasts and homes comes from what they talk about, and, since they are all only kids aged six to twelve, they don't have a whole lot of knowledge about their circumstances. We can infer from Piggy and Ralph's initial conversation at the start of the novel that they were being evacuated; Piggy recalls a man with a megaphone directing them onto the plane and claims he heard the pilot say that an atomic bomb went off and everyone is now dead. So Piggy, at least, understands the idea that there is possibly no home to go back to.

Still, these are young boys and, as the excitement and novelty of their experience starts to run out (at least for some of them), the idea of home and rescue takes on more importance. For Piggy, least liked and in the most danger due to his physical limitations (he can't swim, wears glasses, and suffers from asthma), the prospect of rescue and home is life or death.

One other thing to consider is that "home" is talked about far less than "rescue." The boys who most want to leave seem less concerned with their specific homes and families and more concerned with getting away from the dangers of the island and the wildness that starts to emerge in their fellow castaways.