At the end of the movie, it showed everybody saying goodbye to Mr. Holland, yet he told the principal that he was going to fight the decision.. I guess he decided not to fight it? And why fight it? He was sixty years old, he could have retired in two short years.
"Duh. You're the idiot. Not me."
They showed him fighting it. When he was there talking to the school board, telling them how lazy they had become...that was his fight.
He even says why he's fighting it during that scene. It's not because of his job, he's fighting for the students and their need to have an education in things other than the basics.
Fighting doesn't always involve guns knives or fists