A rock band named No Vacancy takes the stage at a nightclub, just three weeks shy of their audition for the Battle of the Bands competition. The lackluster performance becomes even more chaotic as the slacker guitarist, Dewey Finn, played by Jack Black, attempts a reckless stage dive that ends in disaster. When Dewey awakens in the apartment he shares with Ned Schneebly and his overbearing girlfriend, Patty Di Marco, he learns he must either pay his overdue rent or vacate the premises.
In an unexpected twist, during a rehearsal, Dewey discovers he has been kicked out of No Vacancy, replaced by the new guitarist, Spider. While trying to sell his gear to cover rent, he receives a call from Rosalie Mullins, the principal of Horace Green prep school, inquiring about a substitute teaching position for Ned. Desperate for money, Dewey impersonates Ned and lands the job, adopting the alias "Mr. S" since he can't even spell Schneebly. His erratic behavior on the first day leaves the students bewildered.
The following day, during music class, Dewey overhears the students and crafts an ambitious plan to form a new band to audition for the competition. He selects Zack Mooneyham for lead guitar, Freddy Jones on drums, Katie to play bass, Lawrence on keyboards, and takes on the role of lead vocalist himself. The rest of the class is assigned various responsibilities, with the diligent Summer Hathaway as band manager. This project shifts focus from standard lessons and allows the students to embrace their talents, bolstering their confidence with rock and roll.
As Dewey uplifts Lawrence's spirits, who feels out of place, and helps Zack navigate his strict father's disapproval of rock music, the heavyhearted Tomika, hindered by self-esteem issues, is encouraged to showcase her powerful voice. Two weeks into his stint as their teacher, he sneaks the main band members out for an audition at Battle of the Bands, all while keeping up the ruse that they are still in class.
Upon discovering that they can't perform due to a full lineup, a clever plan by Summer emerges, suggesting they convince the organizers that the kids are battling a terminal illness. This ruse succeeds, allowing them to prepare for the competition under the newly christened band name, The School of Rock. Tension arises when Rosalie comes to inspect Dewey's teaching efficiency, warning him about the upcoming parents' night before the competition, which heightens his anxiety about the charade.
As Dewey gears up for the parents' night, the truth begins to unravel when Ned finds out about Dewey’s impersonation through an unexpected paycheck. The parents, concerned about the unconventional teaching methods, confront Dewey during the meeting. Just when things reach a boiling point, with the arrival of Ned and Patty alongside police, Dewey's true identity is revealed. He rushes home for a confrontation with Patty and Ned, where he confesses his undying love for music. Ned, reminiscing about his past with rock band Maggot Death, encourages Dewey to pursue his passion.
In a climactic turn of events, when parents angrily seek Rosalie regarding the missing kids, the determined students escape school grounds, aiming for the Battle of the Bands competition. Despite protests from Patty, Ned stands firm and decides to support the kids, witnessing them perform at the event. As they play an original song by Zack, their talent shatters initial doubts, with the crowd roaring in support. Although Dewey's former band, No Vacancy, eventually wins, the audience demands an encore from The School of Rock, who respond with "It's a Long Way to the Top (If You Wanna Rock 'n' Roll)" by AC/DC.
In a surprising twist of emotions, the previously upset adults in attendance, including Ned and Rosalie, find themselves filled with pride and admiration for Dewey and the students’ spectacular performance. Fast forward to the future, the School of Rock has transformed into a thriving after-school program, with the ambitious Summer navigating multiple performance opportunities for the band. Dewey, now residing independently, continues to mentor his students, while Ned breaks free from Patty's grip to embark on teaching young musicians himself.
