Dewey Finn (Jack Black) is a rock musician who is over 30 years old but still working hard for his ideals. He disdains the kind of shoddy and hypocritical music full of commercial flattery, and is dedicated to pursuing pure rock music with true feelings. For this reason, he parted ways with countless bands, has not achieved any success in his career so far, and is facing the dilemma of being driven out by the landlord. Dewey's male landlord and old friend Ned Schneebly (Mike White) was previously a fanatical and restless death rock musician, but now he has transformed himself into a good family man and substitute teacher. When Dewey was idle at home, he accidentally received a recruitment call from a middle school, and the other party invited Ned to come to the school as a substitute teacher. Dewey, who was extremely bored and forced to make a living, changed his identity and entered this prestigious middle school with a very rigorous school spirit to teach as Ned. The students' lifelessness once made him feel bored. One day, Dewey accidentally discovered the children's musical talent. So, he deceived everyone and led these children who only knew how to study into a new and fun rock world...