What does the First Academy Building symbolize in A Separate Peace by John Knowles?

At the beginning of A Separate Peace by John Knowles, Gene returns to Devon 15 years after he graduated high school. When he visits the First Academy Building, he narrates,

In through the swinging doors I reached a marble foyer, and stopped at the foot of a long white marble flight of stairs. . . The marble must be unusually hard. . . It was surprising that I had overlooked that, that crucial fact. I had more money and success and "security" than in the days when specters seemed to go up and down them with me (11-12).

Not only do these hard marble stairs represent Gene's many days at school and his youth, but they are part of the reason his friend Phineas died in high school. It is in the First Academy Building that Brinker holds a mock trial to accuse Gene of breaking Finny's leg the first time. Phineas becomes angry because of the trial and storms out, slips on the marble, and breaks his leg a second time on the stairs. The fact that Gene notices how hard the marble stairs truly are 15 years later helps him realize part of the reason behind Finny's leg breaking a second time. At the time, however, Gene says the following about the marble and the building:

The excellent exterior acoustics recorded his rushing steps and the quick rapping of his cane along the corridor and on the first steps of the marble stairway. Then these separate sounds collided into the general tumult of his body falling clumsily down the white marble stairs (177).

The above passage describes how Phineas breaks his leg months after the first break. Gene harbors some guilt because he caused the first break by jouncing Finny out of the tree near the river the previous summer. Phineas would never have been able to go to the war after his first break; after the second break, complications after surgery take his life. Therefore, the marble stairs in the First Academy Building partially represent Gene's past; but for the most part, the stairs represent the end of his friendship with Phineas. Fortunately, Gene has some time to talk about their friendship and clear the air before Finny dies. Visiting the First Academy Building years after this life-changing event is meaningful for Gene because it is in this building that Finny's end is fatally decided. It's as though Gene pays homage to his friend by visiting the location of Finny's second accident. Again, noticing the hardness of the stairs reaffirms to Gene that Finny's death wasn't his fault. This brings him some peace, but he certainly views the First Academy Building as a sacred place where a good friend's accident eventually took his life.