The setting of A Separate Peace – both time and place – are integral to the story and its meaning. As you'll read, well, everywhere in this guide, the backdrop of World War II establishes a series of parallels with the daily lives of the boys at Devon. "War" is both a military and personal term. (Gene fights a war against his own jealousy and fear, he identifies Finny as the enemy, and the boys all struggle against their personal demons.)
As far as place is concerned, Devon is presented as an almost Edenic paradise. (Edenic = Eden-like. Get used to it, you'll see this word a lot in literary criticism.) The trees, the animals, the peaceful, lazy rivers – you get the picture. Notice how the war slowly creeps into the academy, starting with recruiters and ending with troops in Chapter Thirteen? Devon's initial isolation from the rest of the world is as important as its peaceful atmosphere. The boys are physically sequestered from adults and from war, but this barrier is an impermanent one.