Dewey Finn (Jack Black) loves to rock, but he doesn't like to work. When he is kicked out of the band that he formed he doesn't know exactly what to do, but sets out to start a new band. Unfortunately for Dewey his roommate's uptight girlfriend Patty (Sarah Silverman) convinces his roommate, Ned Schneebly (Mike White), that Dewey needs to start paying some of the bills. When a school calls requesting his roommate's services as a substitute, Dewey decides that this is an easy chance to make some money and get Patty and Ned off his back. After meeting the students and noting that many of them have musical talents which he might utilize in his new band he begins a top secret project to convert them into his new band. The children are quickly engaged in this project and must find ways to hide their efforts from the school principal Rosalie Mullins (Joan Cusack), and their parents. Soon enough their time comes to show of what they have learned in the 'School of Rock'.