"Make your lives extraordinary".

Set in 1959, the film tells the story of the English professor John Keating  who inspires his students to a love of poetry and to seize the day through his unconventional teaching methods. The place is Welton Academy in Vermont, a school which is based on the four principles: "Tradition, Honor, Discipline and Excellence". Into this atmosphere comes Keating, himself a Welton alumnus, who works hard to encourage his pupils to think freely.

To understand the reference to "O Captain! My Captain!" click on this link and hear the poem and read the meaning. Todd is comparing his ex-teacher with Abraham Lincoln, the victorious general now dead.

You can also watch this video with subtitles here.

MR. NOLAN: What is poetry?
CAMERON: That page has been ripped out, sir.
MR. NOLAN: Well, borrow somebody else's book.
CAMERON: They're all ripped out, sir.
MR. NOLAN: What do you mean, they're all ripped out?
CAMERON: Sir, we, uh...
MR. NOLAN: Never mind... Read!
CAMERON: "Understanding Poetry by Dr. J Evans Pritchard, Ph.D. To fully understand poetry, we must first be fluent with its meter, rhyme and figures of speech, then ask two questions: one, how artfully has the objective of the poem been rendered and two..."

... "How important is that objective? Question one rates the poem's perfection; question two rates its importance. And once these questions have been answered, determining the poem's greatness becomes a relatively simple matter. If the poem's score for perfection is plotted on the horizontal of a graph..."
TODD: Mr. Keating! They made everybody sign it.
MR. NOLAN: Quiet, Mr. Anderson.
TODD: You gotta believe me. It's true.               
KEATING: I do believe you, Todd.
MR. NOLAN: Leave, Mr. Keating.
TODD: But it wasn't his fault!
MR. NOLAN: Sit down, Mr. Anderson!... One more outburst from you or anyone else, and you're out of this school!    Leave, Mr. Keating... I said leave, Mr. Keating.           
TODD: O Captain! My Captain!
MR. NOLAN: Sit down, Mr. Anderson! Do you hear me? Sit down! Sit down! This is your final warning, Anderson. How dare you? Do you hear me?
KNOX: O Captain! My Captain!
MR. NOLAN: Mr. Overstreet, I warn you! Sit down!... Sit down! Sit down. All of you. I want you seated. Sit down. Leave, Mr. Keating... All of you, down. I want you seated. Do you hear me?... Sit down!
KEATING: Thank you, boys. Thank you.

A demonstration of the allegiance for the teacher who not only instructs, but also changes his student's lives, in a moving tribute to his teaching.

Mr. Keating referred to Walt Whitman during one of his lessons...
"O Captain, my Captain. Who knows where that comes from? Anybody? Not a clue? It's from a poem by Walt Whitman about Mr. Abraham Lincoln. Now in this class you can either call me Mr. Keating, or if you're slightly more daring, O Captain my Captain."
At the end of the film, the students show their support to the recently-dismissed Keating in defiance against the school's headmaster, by calling the phrase in the classroom.