Richard Dadier (Glenn Ford) is a new teacher at North Manual Trades High School, an inner-city school of diverse ethnic backgrounds where many of the pupils, led by student Gregory Miller (Sidney Poitier), frequently engage in anti-social behavior. Dadier makes various attempts to engage the students' interest in education, challenging both the school staff and the pupils. He is subjected to violence as well as duplicitous schemes; he first suspects Miller, but later realizes that Artie West (Vic Morrow) is the perpetrator, and challenges him in a tense classroom showdown involving a switchblade knife.