It shows that Jack rules by fear and violence.
Simon retrieved Piggy's glasses for him, after they had fallen onto the rocks as a result of Jack punching Piggy.
he gets knocked out
Jack took Piggy's glasses.
Jack and his followers steal piggy's glasses.
Roger and Maurice are the ones that attack Jack and Piggy because Jack wants Piggy's glasses.
piggy's glasses
After Jack leaves to go to Castle Rock, Piggy becomes more confident with himself, and starts to stand up for himself. This happens because Jack stole Piggy's glasses, and now he can no longer hide behind his disability of not being able to see.
Jack shows his power over Piggy from the very first time they meet when he tells Piggy to shut up. Throughout the book Jack continually speaks dismissively to Piggy, telling him that he isn't wanted on the expedition to the mountain, calling him a fat slug during a meeting and continually belittling the fat boy. Piggy is fully aware that Jack hates him and Jack makes this abundantly clear for everyone to see. Refusing to give Piggy any meat and punching him are two further examples of Jack demonstrating his power and physical prowess over the fat and ineffectual Piggy.
Piggy helping to gather firewood after Jack breaks away from the group symbolizes a shift in power dynamics within the group. It shows Piggy's willingness to step up and contribute, even when faced with adversity. This moment highlights Piggy's growing independence and confidence as he asserts himself in the group's hierarchy.
Piggy
Jack initially dismisses Piggy and the influence he has on the group. He belittles Piggy's intelligence and continually undermines his authority in order to maintain control over the other boys on the island. Eventually, Jack's treatment of Piggy escalates into physical violence, culminating in Piggy's tragic death.
Jack orders the boys to kill Piggy and Ralf.