Peer pressure is a driving force in much of the action throughout A Separate Peace. Many of the episodes in the book are shaped by the reactions of the boys to challenges by one of the others.
Finny decides he's going to break the rules and jump out of the tree, and does so. Upon surfacing, he begins the pressure. "Who's next?" Gene, scared of the height and of breaking the rules, reluctantly follows.
What was I doing up here anyway? Why did I let Finny talk me into stupid things like this? Was he getting some kind of hold over me?
After Gene jumps, Leper rates Gene's jump as "better than Finny's" but he "became inanimate" in refusing to give in to Finny's pressure to take his turn as a jumper. Chet Douglas and Bobby Zane give voice to their reasons, but also refuse to bow to Finny's demands.
Finny breaks the school swimming record, but then discounts the accomplishment with the comment, "The only real swimming is in the ocean...Let's go to the beach." Again, Gene is faced with peer pressure.
The beach was hours away by bicycle, forbidden, completely out of all bounds. Going there risked explusion, destroyed the studying I was going to do..., and it also involved the kind of long, labored bicycle ride I hated. 'All right,' I said.
In possibly the supreme achievement of their time at Devon, Gene and Finny even succeeded in pressuring Brinker, the ultimate supporter and enforcer of the rules. As Brinker attempts to make a mockery of the approaching Winter Carnival, Gene points out how much Finny is anticipating the celebration. Brinker attempts to argue against the idea.
there's never been a Winter Carnival here. I think there's probably a rule against it.' 'I see," I said in a tone which made Brinker raise his eyes and lock them with mine. In that plotters' glance all his doubts vanished, for Brinker the Lawgiver had turned rebel for the Duration.
Leper was the one of the boys who most often resisted the force of peer pressure. When volunteers were needed to shovel out the train tracks, "two hundred volunteers" were requested from Devon School. Gene and several of his closest friends were among those agreeing to go, including, to Gene's surprise, Quackenbush. Leper, however, went cross-country skiing - partly because he probably hadn't heard the call for volunteers, partly because he lived true to his own personal interests rather than for the others.