Horror High(1973)

A nerdy high school super whiz experiments with a chemical which will transform his guinea pig "Mr. Mumps" from a gentle pet into a ravenous monster. In a fit of rage against his tormentors at the high school, Vernon Potts goes on a killing spree, eliminating all of those who ever picked on him - the Gym Coach, the School Jock, The Creepy Janitor & his hated teacher, Ms. Grindstaff.