Gabriel Kotter is a teacher in Brooklyn, New York who ends up teaching at his old alma mater: Buchanan High School. He has been assigned to teach the remedial students, better known as the Sweathogs, a group to which he used to belong.
When it is announced that Horshack has graduated out of the Sweathogs and into regular classes, Kotter instructs the remaining Sweathogs to shun him so that he can meet people in his new classes.