<Li> Lance Lim as Zack, a 12 - year - old schoolboy who is best friends with Lawrence and Freddy . He plays the electric guitar . </Li> <Li> Aidan Miner as Lawrence, a 12 - year - old schoolboy who is best friends with Zack and Freddy and is considered the smartest kid in his class . He plays the electronic keyboard . </Li> <Li> Tony Cavalero as Mr. Finn, the new substitute teacher and an ex-rock musician who teaches the kids how to play and work together as a band . In the second season, he is promoted to a regular teacher . </Li> <Li> Jama Williamson as Principal Mullins, the principal of the school . In the first season, she is a recurring character, but is promoted to a main character in the second season . </Li>

Who plays mr finn on school of rock