After once again neglecting to finish his
homework, Horrid Henry has his friend, Brainy Brian, forge a note from his mother claiming that his cat ate it. His teacher, Miss Battle-Axe, sees through Henry's ruse because the word "homework" is spelled correctly, something Henry struggles with. While Henry is in detention, his friends join him, and they rehearse for a
school talent contest; they are interrupted by Miss Oddbod, the
Headmistress, and two school inspectors. Meanwhile, Vic Van Wrinkle, the corrupt headmaster of the prestigious Brick House School, influences the school inspectors to close Ashton Primary, the school Henry attends, hoping to profit from an influx of new students. The inspectors encourage Henry's pranks and even frame him, resulting in Miss Battle-Axe and her colleague, Miss Lovely, being
dismissed for failing to enforce discipline. Furthermore, Miss Oddbod prohibits Henry's band, the Zero Zombies, from entering the talent contest. With Ashton Primary on the brink of closing, Henry's Great Aunt Greta offers to pay for Henry to attend an all-girls private academy—thinking Henry is a girl—and his younger brother, Perfect Peter, to attend Brick House. Miss Lovely applies for a job at Brick House and spies on Van Wrinkle; she is captured, but passes notes about Van Wrinkle's plan to Peter. After Henry escapes from his new school with the help of Margaret, who has also been transferred there, he and the Zero Zombies perform in the talent contest and win. Henry thinks that their victory will garner enough fame to keep Ashton Primary open, but Miss Oddbod tells him that fame alone cannot change the school's fate. Henry later receives an invitation to compete on the
game show 2Cool4School, and Margaret realizes that the cash prize could be used to bribe the school inspectors into leaving Ashton Primary alone. In the final round of the game, Henry is confronted by Miss Battle-Axe, who challenges him to spell "homework". Using Miss Battle-Axe's phrase "Oh, Henry" as a
mnemonic device, he finally spells the word correctly and wins. To Henry's surprise, Miss Battle-Axe reveals that she is a former
2Cool4School champion herself and she used her connections to orchestrate Henry’s appearance on the show. Meanwhile, Peter and his friends try to rescue Miss Lovely, but are captured by Van Wrinkle. Miss Lovely tricks Van Wrinkle into explaining his plan while Peter has her mobile phone on a call with Miss Oddbod, who contacts the police. Van Wrinkle attempts to escape, but falls over due to Peter tying his shoelaces together; he and the school inspectors are arrested. Miss Oddbod declines the cash prize, which is instead used to throw a large party at Henry's house. ==Cast==