Max Keeble, a young paperboy, is getting ready for his first year in middle school, and he wishes to become cool after being a nerd in previous years. He constantly faces off against the Evil Ice Cream Man, who pretends to be a bionic supervillain while he is really just a cheap ice cream vendor. The principal, Elliot Jindrake, hates children and plots to demolish Max's beloved animal shelter so that he can become the next chairman after the current one, "Crazy Legs" Knebworth, retires. Max, alongside his best friends, Megan and Robe, are frequently bullied by former childhood friend Troy McGinty and former millionaire Dobbs. At his first day of school, Troy launches Max to a dumpster and he had to attend to the school assembly covered in trash. Then Dobbs steals Max's lunch money, which Mrs. Styles let him do by thinking it's an investment advice.
After Jindrake announces that he will be building a new football stadium and recruited European exchange students, there has been a mysterious budget cut in which there aren't enough money for textbooks, musical instruments, medicines, and food. As well Max investigates who will close the animal shelter and Jindrake admits in his face also that he will because he hates children and animals, and he is willing to get rid of the animals and punish everyone unfairly.
Max' father, Don Keeble, acts in embarrassing commercials, but he gets a promotion. Eventually, this forces his family to move to Chicago in a week besides of Max's and his mother Lily|'s objections. The next day, Troy puts Max in the toilet, and when he's late for class, Mrs. Styles punishes him with an essay even it isn't his fault. Then he comes to think that he can get revenge on his bullies as he will be gone for when they find out what he did and asks Robe and Megan to help him get revenge. First, Max steals a metal coil from the Evil Ice Cream Man's truck and places it on Dobbs' doorstep. Then he steals Dobbs' handheld, and frames the Evil Ice Cream Man for it. When the Evil Ice Cream Man is hated and insulted by young customers, and his ice cream begins to melt, he hears that it was Dobbs' fault, and when Dobbs confronts him about stealing his handheld, they insult each other by destroying the items. Then in the junkyard, Max uses the excavator to lift the ice cream truck and splash them with the melted ice cream.
Later Max and Robe get revenge on Troy by using his greatest fear, McGooggles the frog (a Scottish Barney-like mascot frog). They play the McGooggles song when he opens his locker. Then Max puts on Don's old McGooggles costume and locks Troy in the gym with him. Then the gym class finds him in fetal position shivering and he's humiliated by admitting his fear. He even has to take psychological therapy to recover.
For final touch, Max, Megan, and Robe broke into Jindrake's office, rigs the capitol background with a mocking picture of Max in it, puts animal pheromones in Jindake's breath spray, checks his computer, and finds out that he embezzled 96% of the school budget to build his football stadium. Later at school, Superintendent Knebworth comes to inspect the school so Jindrake could be promoted to take his place, but the animals in the shelter smell the pheromones in his breath spray and started attacking him. At the same time, Max starts a food fight to make Jindrake look bad. The chimp from the shelter then knocks Jindrake and starts to hop on him, Knebworth leaving in disgust.
Max had promised to have a farewell party with Megan and Robe, but instead he goes to a milkshake one that is hosted by his love interest, Jenna, and ditches his friends, when they find out, they feel betrayed and that he was using them to get revenge on the bullies. When he tries to apologize, much to his surprise, Don quits his job after Max advises him to not be pushed around by his boss and decides to stay home to start his own business, unknown to him of Max's recent actions. Later Max's victims find out what he did, and Megan and Robe are suffering because of the vengeance. Even worse, Jindrake is going to punish everyone for Max's actions. Then Max breaks into Jindrake's office and uses his camera to apologize to everyone including Megan and Robe, and to dare Dobbs and Troy to a final standoff. Jindrake returns and menaces him with an extremely grave punishment for his actions, unbeknownst that he used his camera to make him confess his embezzlement of the school budget.
Jindrake locks Max in the janitor's closet but he manages to escape in time for the standoff. He give a short fight that is then interrupted by Megan, Robe, and the rest of the students who gather around Troy and Dobbs playing We're not gonna take it, being fed up with their abuses, and going to get revenge on them as well, ready to throw them in the dumpster together, but Max tells everyone that they will be like the bullies and that they should let them go (and let them fall in the dumpster). Jindrake gets a bulldozer ready to run over the kids and tear the shelter apart, but Max gets there in time to release the animals to chase Jindrake's pheromone smell. Finally, the shelter gets saved, Jindrake got fired for embezzleing the school budget, and the bullies are now nice because they fear their former victims to turn against them again. The Evil Ice Cream Man chases Max in the final scene of the film.
- Alex D. Linz as Max Keeble
- Zena Grey as Megan
- Josh Peck as Robe
- Noel Fisher as Troy McGinty
- Robert Carradine as Don Keeble
- Nora Dunn as Lily Keeble
- Jamie Kennedy as Evil Ice Cream Man
- Larry Miller as Principal Elliot T. Jindrake
- Orlando Brown as Dobbs
- Justin Berfield as Caption writer
- Brooke Anne Smith as Jenna
- Chely Wright as Mrs. Styles
- Myra as Chelsea
- Kyle Sullivan as Techie kid
- Tony Hawk as Himself
- Lil' Romeo as Himself
- Clifton Davis as Superintendent Bobby Knebworth
- Amy Hill as Ms. Phyllis Rangoon
- Amber Valletta as Ms. Dingman
- Veronica Alicino as Mrs. Talia
- Martin Spanjers as Runty Band Member
- Adam Lamberg as Student on Motorcycle
- Countess Vaughn as Office Admin. Assistant
- Dennis Haskins as Mr. Kohls
- Marcus Toji as Food Fight Chess Player
- Marcus Hopson as Pizza Parlor Kid
- When Jindrake introduces himself to Max after locking him in the closet, he says "Here's Jinny", which is a reference of The Shining line "Here's Johnny!".
- Caption Writer is also known as Reese from Malcolm in the Middle.
- Robe is also known as Josh Nichols from Drake & Josh, which is ironic as Drake & Josh also featured a character called Megan.
- Dobbs is also know as Eddie Thomas from That's So Raven.