An alcoholic man’s life has changed when he goes into recovery when he becomes a teacher at a school he graduated from.

Things are very unclear, mostly with the inciting incident. What is it? Is it going into recovery or going to his old Ivy League? Also there's no need to include "Man" in the logline since you refer to him with him/his pronouns. Is he inspired to go into recovery because he attends his old school? Or is he inspired to go to his old school after going into recovery?

It also feels like something is missing regarding his recovery, since alcoholics tend to have a catalyst in their lives that inspires them towards this goal.

The other thing that's unclear is the goal. He goes into recovery and attends his old school, then what?

Leaning towards:
“A recovering alcoholic turns to a life redeemed when he becomes a teacher at his alma mater.”

Take care.