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 man. 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 Max had to attend to the school assembly covered in trash, then Dobbs steals Max's lunch money and a teacher let him do it by thinking is an investment advice.
After Jindrake announced 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 text books, musical instruments, medicines, and food. As well Max investigates who will close the animal shelter and Jindrake admitted in his face also that he will, and 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 mom's objections. The next day, Troy puts Max in the toilet, and when he gets late for class, the teacher punish him with an essay even it wasn't Max's 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 asked Robe and Megan to help him get revenge. First, Max steals a metal coil from the Evil Ice Cream Man's truck, places it in Dobbs' doorstep, and 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 were playing the McGooggles song when he opens his locker and Max was wearing his dad's old McGooggles costume and locked Troy in the gym with him. Then the gym class found Troy in fetal position shivering and is humiliated by admitting his fear, he even had to take psychological therapy to recover.
For final touch, Max, Megan and Robe broke into Jindrake's office, rigged the capitol background with a mocking picture of Max in it, put animal pheromones in Jindake's breathe sprays, checked his computer, and found out that he embezzeled 96% of the school budget to build his football stadium. Later at school, Superintendent Knebworth came to inspect the school so Jindrake could be promoted to take his place, but the animals in the shelter smelled the pheromones in his spray and started attacking him, at the same time, Max started a food fight to make Jindrake look bad, the chimp from the shelter then knocked Jindrake and started to hop on him, Knebworth left in disgust.
Max had promised to have a farewell party with Megan and Robe, but instead he goes to a milkshake party that is hosted by his love interest, Jenna, and ditched his friends, when they found out, Megan and Robe felt betrayed and that Max was using them to get revenge on the bullies. When Max tried to apologize, much to his surprise, Don quits his job after Max adviced him to not be pushed around by his boss and decided 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 was going to punish everyone for Max's actions. Then Max broke in Jindrake's office and used his camera to apologize to everyone including Megan and Robe, and to dare Dobbs and Troy to a final standoff. Jindrake returned to his office and menaced Max with an extremely grave punishment for his actions, unbeknownst that Max used his camera to make him confess his embezzelment of the school budget.
Jindrake locked Max in the janitor's closet but he manage to escape in time for the standoff, Max give a short fight that is then interrupted by Megan, Robe, and the rest of the school who gather around Troy and Dobbs playing We're not gonna take it, being fed up with their abuses, the whole school were going to get revenge on them as well, ready to throw them in the dumpster together, but Max tell 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 in time to release the animals to chase Jindrake's pheromone smell. Finally, the shelter got saved, Jindrake got fired for embezzeling the school budget, 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
- Myra as Chelsea
- Kyle Sullivan as Techie kid
- Tony Hawk as Himself (cameo)
- Lil' Romeo as Himself (cameo)
- Clifton Davis as Superintendent Bobby "Crazy Legs" 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