Professor William Hundert is a distinguished Classics history teacher at St. Benedict's Academy for Boys. Another year is beginning, and the students file in and introduce themselves. Hundert has a certain plaque above his door he requires one student, Martin Blythe to read. The plaque states: "I am Shutruk Nahunte, King Anshand and Sussa, sovereign of the land of Elam. By command of Ishushinck I destroyed Sippar, took the stele of Niran-Sin, and brought it back to Elam, where I erected it as an offering to my god, Inshushink." He requires his students to look up Shutruk Nahunte, then stops them, saying they won't find it in any history book, because Nahunte is not any. Hundert then says that Nahunte was virtually forgotten because "Ambition and conquest without contribution is without significance." Then he challenges his students, saying "What will your contribution be? How will history remember you?" which becomes the theme of the film. A friendly relationship between Hundert and fellow teacher Elizabeth is also introduced, as she has returned from Greece and presents Hundert with a snow globe of the Parthenon.
A new student enter the fray shortly after, a certain Sedgewick Bell, the son of a senator from West Virginia. The cocky Bell starkly contradicts the principled Hundert, and various acts of rebellion lead to much tension between the two. As Bell's attitude worsens, and Hundert unable to straighten him, Hundert feels forced to travel to Washington D.C. and have a word with Senator Bell, Sedgewick's father. The Senator shows a surprising amount of apathy in his son's character development, and reprimands Hundert, telling him that Hundert's job is to teach him facts out of a text book, but not to influence him as a person. Hundert dejectedly returns to St. Benedict's and begins preparations for a certain "Mr. Julius Caesar" contest. The three finalists are determined by a series of essays given by Hundert, and the three highest net scores proceed to the finals, where they stand on stage in togas and answer trivia questions about ancient Roman history. During the course of the essays, Hundert surprisingly sees a changed Bell, one who begins working hard in his studying and overachieves Hundert's expectations. After Hundert completes the grading of the essays, Deepak Mehta, Louis Masoudi, and Martin Blythe have the highest score. However, wanting to reward a newly-dedicated Bell, Hundert alters his grade, putting him ahead of Blythe.
The Mr. Julius Caesar contest arrives and Masoudi, Mehta, and Bell are pitted against each other. Masoudi quickly misses a question and is forced to sit, leaving Bell and Mehta to duel each other for the crown. Both do surprisingly well, much to Hundert and Bell's father's excitement. However, Hundert notices Bell does a peculiar motion whenever he is asked a question, where he put his hands over his eyes. Hundert speculates Bell is cheating and quietly asks the headmaster what to do. Contradictory to Hundert's principles, the headmaster tells Hundert to allow it. Knowing Mehta read an extra-curricular book about Hamilcar Barca, who is not in the assigned textbooks, Hundert asks Bell a question about him. Surely enough, Bell can't answer and Mehta wins the crown of Mr. Julius Caesar. Hundert visits Bell later and discovers that Bell indeed was cheating, having taped notecards of the question on his toga, out of sight to anyone but him. Hundert keeps the incident to himself but the trust and respect he had developed for Sedgewick has been broken. Hundert feels he has failed as a teacher, especially considering he disallowed Blythe from participating.
Twenty-five years later, Hundert and Elizabeth are married, and the headmaster of St. Benedict's has passed away. Thinking he'll take the vacated position, Hundert is shocked to discover a fellow teacher has been given the privilege of being named the headmaster, because the Board believes he's a better fundraiser. Hundert immediately tenders his resignation, much to the Board's chagrin, and retires. Shortly after, Hundert receives a letter inviting him to a class reunion, one that a now-successful and wealthy Sedgewick Bell is hosting. Also, if Hundert agrees to come and host a rematch of the Mr. Julius Caesar contest, Bell will donate a large amount of money to the school. Agreeing to this, Hundert arrives at Bell's estate, where an enthusiastic Bell greets Hundert. Before the rematch begins, Bell speaks of Hundert's dignity and how much Hundert taught him, in spite of his rebellious nature. Then, Bell reveals his attentions to succeed his late father and run for Senator, and the contest begins.
Once again Masoudi loses on the first question and Mehta and Bell duke it out again. Both again do surprisingly well, but Hundert catches a glimpse of an earpiece in Bell's ear, then looks to the back and sees a man on a headset looking in books. Shocked, Hundert continues the contest, but asks Sedgewick Bell who Shutruk Nahunte was, knowing Nahunte isn't in any textbooks. Both Bell and the man on the headset are stumped, but Mehta quickly recites the plaque that was above Hundert's wall, and wins the contest again.
Hundert goes to the bathroom to collect himself, and Bell walks in, engaging Hundert in pleasant conversation, which Hundert uses to confront Bell. Suddenly Bell's demeanor changes and he becomes defensive and spiteful, telling Hundert that he doesn't care for Hundert's principles and virtue, because it's all a bunch of bull****. Bell reveals he lives in a world where "people do what they do to get what the want." Suddenly, Bell's son emerges from a stall with a shocked look on his face, and quietly walks out. Bell is left speechless and embarrassed, knowing he just revealed himself to be a cheater and liar in front of his son. Hundert quietly retires to his room, and wakes up the next morning expecting to find his students down at breakfast. Reading a note they left wishing him well, and disappointed by their absence, he prepares to leave, but they throw a surprise party in his room when he returns, and Hundert later admits to a now-grown Martin Blythe that he allowed Bell to unfairly sneak over him in the Mr. Julius Caesar contest years earlier.
Upon returning to his home, he decides to return to St. Benedict's, now a co-ed school, as a teacher of the Classics. It shows a fresh new batch of students, including Martin Blythe's son. Seeing Martin Blythe outside his classroom window and exchanging a friendly wave, Hundert has Blythe's son read Shutruk Nahunte's plaque, just as his father did years earlier.