The last scene of the novel involves a moment of situational irony as Headmaster Nolan teaches English after firing Mr. Keating, who has entered the classroom to gather his things:
The irony of Nolan’s choosing the Pritchard essay just as he walked in the room was just too incredible.
Headmaster Nolan chooses to begin his class the same way Mr. Keating began his second class in Chapter 5: with an essay by Pritchard detailing how to evaluate poems. Mr. Keating, however, made the class rip the essay out of their textbooks, believing the essay to be valued only by the "academic hoi polloi." Kleinbaum rightfully acknowledges the irony of the situation—though he doesn't realize it, Mr. Nolan is embodying the “academic hoi polloi” whom Mr. Keating believes to entirely miss the point of poetry. Mr. Keating’s emphasis on passion and individuality is at odds with Headmaster Nolan’s focus on success and conformity. Mr. Keating’s earlier command to rip out the essay—which appeared at the time to be a theatrical means of conveying the idea that poetry is about passion—was in fact a necessary prophylactic against the academic hoi polloi, whether or not he knew it at the time.
The irony of the situation also amusingly highlights the growth of the students. They no longer fit in at Welton, and without the Pritchard essay they are literally unable to be educated in the boring and conformist way Nolan, the story’s antagonist, would like them to be. Immediately following this moment of irony, Todd inspires the rest of the students to stand up on their desks in tribute to Mr. Keating, reenacting their earlier class in which Mr. Keating urged the students to stand on their desks to view the world from a different perspective. With Mr. Keating gathering his things and Nolan serving as interim teacher, the students endorse Mr. Keating's pedagogical approach by standing on their desks, shouting “O Captain! My Captain!”, and refraining from reading the essay that they have removed from their textbooks.