Why wasn't Holden at the big football game?
Holden gives two reasons for not attending the football game. The first is that he and the rest of the fencing team had gone to New York for a fencing competition. They were meant to be gone until the evening, but Holden forgot the fencing equipment on the subway and they had to return without getting to compete. Holden seems to think this is "pretty funny," but the rest of the team sure doesn't and "ostracizes" him the whole way back.
Since the team was back in time for the game after all, Holden could have gone to it, but he goes instead to say goodbye to his history teacher, Mr. Spencer. Since Holden is being kicked out of Pencey, Spencer wanted to say goodbye and give him a lecture/pep talk about what he's doing with his life, which Holden hates.