While the boys in "A Separate Peace" initially were either ambivalent or persecutory toward Leper, there is a great transition of those attitudes as the story progresses.
For instance, once Leper goes into the army, the boys begin noting all the wartime headlines about victories, and they credit Leper for each one. Their imaginations run wild with ideas about who he could be fighting or battles he could be winning.
Once Gene has a very intimate talk with Leper toward the end of the story, he discovers that his friend received a "Section Eight" discharge, reserved only for those who are mentally unstable. Leper describes his intense hallucinations to Gene, and Gene is so distraught by the descriptions of severed body parts and unreal visions that he abandons Leper at his home.
Throughout the story, Leper is somewhat of an "outcast," hence the symbolism behind his name. Lepers in biblical times were scorned and shunned for their physical condition, a pox-like infection that spread rampantly throughout that time and place. They, too, were considered outcasts.
Leper is different from the other boys, and the other boys at school either ignore him or make fun of him.
Leper Lepellier is a student who likes science projects and snails; he is not athletic and is indifferent to competitive sports and the rough-and-tumble activities preferred by the others. Leper's peers see him as eccentric, and Gene refers to him as "little lily-livered Lepellier" before Gene and Finny climb the tree on the evening of Finny's fateful accident (Chapter 4). As Gene gets to know Leper a little better, especially during the time Finny is absent from school, he begins to appreciate Leper as a person in his own right. Gene begins to understand the dynamics of social interaction among high school youth, and the tendency for the stronger, more popular students to scorn those among them who are different. He especially recognizes this inclination within himself, and, once aware of it, struggles to overcome it. Gene says that "with Leper it (is) always a fight, a hard fight to win when you (are) seventeen years old and (live) in a keyed, up, competing school, to (avoid) making fun of him...but as I (have) gotten to know him better this fight (has) become easier to win" (Chapter 7). Gene knows that Leper is an individual who deserves to be respected for whom he is, and, with burgeoning maturity, tries to treat him accordingly.