In A Separate Peace what changes occur between the summer and fall sessions at Devon School?

In Chapter 6 of the novel, Gene discusses the changes at Devon.  He begins by stating, "Peace had deserted Devon" (72). The lackadaisical feel of Devon's first summer school is gone, and the staunch tradition of the old professors has returned with them from their summer leave. Gene's reference to peace possesses two meanings--the school has upped its tempo toward preparing boys for war instead of for peacetime, and the peace that many of the boys felt from the carefree days of summer disappeared with Finny.

As Gene sits in the immutable opening of the fall semester, he thinks in reference to the summer,

"The traditions had been broken, the standards let down, all rules forgotten" (73).

He realizes that life at Devon can never return to Finny's summer world that he created for all of them--a world without boundaries and with all the promise of youth. The school's return to tradition and stifled activity mirrors the conflict inside of Gene.