The play v. the film
It was inevitable that the play Tea and Sympathy would not reach screens without being changed.
According to Vito Russo's book, The Celluloid Closet, in the play, Tom Lee has done nude swimming with a male teacher at the school who is also thought to be gay. This is another reason for him to be scorned. But just the mention of naked swimming was probably enough to make the stage version controversial at that time. Of course, the more censored Hollywood would not dare to show or even allow a verbal reference to such activity. That was to be expected in the uptight fifties. But the absence of the episode in the movie was another way of removing any doubt that Tom was straight but just not able to prove it to his peers.
As Robert Osborn's guest on TCM said, Deborah Kerr objected strongly to the voice-over in the final scene, when Tom is reading her letter. She and John Kerr had starred in the play. In it's last scene, Laura and Tom are in his room.
Laura unbuttons her blouse as she is saying her famous line "Years from now when you talk about this, and you will, be kind". Then the final curtain descends. But the ending to the movie had to reveal Tom as happily married.
Russo points out a detail that I had missed in the first scene. When Tom is walking among his former tormentors at the ten year class reunion, his wedding ring is the largest one of them. Hooray for Hollywood!