Dewey Finn (Jack Black) lives for Rock and Roll. Not that namby-pamby Nirvana stuff, mind you, but hard rock - Black Sabbath, Led Zeppelin, Pink Floyd, Metallica. He dreams of making it big and has devoted everything to his band which makes it hurt even more when his band kicks him to the curb.
Losing this gig is the final straw for his best friends over bearing girlfriend, Patty (Sarah Silverman) and she demands that Ned (Mike White) kick Dewey out. Mike gives Dewey one last chance he has to find a job or get out. Besides Ned tells him, look at him he is a substitute teacher now - he has been able to successfully leave his hard rocking days behind him.
Ned doesn't count on Dewey taking his advice, his identity, and his reputation.
Which is exactly what Dewey does when Rosalie Mullins ( Joan Cusack) calls to offer Ned Schneebly a job. She has heard of his reputation and she needs a substitute teacher for her prestigious private school. Dewey accepts the position and shows up to the school as Ned. He promptly decides that curriculum is too stuffy. The kids don't need to learn Math, they need Rock 101. This is something he can teach and just maybe he can make a rock band out of the kids and then win the local battle of the bands.
Can the kids get it together and when the contest or will it all unravel when the truth about Dewey comes out?