In fact, three years after the OP’s story is set, the unpleasantness of the Johnny Bright Incident takes place.
The nail in the coffin of the “gentleman’s agreement” was when the University of Pittsburgh refused to bench Bobby Grier for the 1955 Sugar Bowl and pressed, moreover, for the Pitt section of the stadium to be fully integrated seating.
This caused the segregationist governor of Georgia to completely blow his stack and demand that Georgia Tech boycott the game. This demand looked ridiculous to most people, and Georgia Tech, to its credit, didn’t give in to the governor. School officials insisted that they had a contract to play the game that they had to fulfill, and students from the school hung the governor in effigy.
This was just a few years down the road - even in 1948, cracks were appearing in the foundations of segregated college football.