Hell High (1989)

The teachers are tough...but their exams are murder.

A teacher with a paranormal gift and a dark past, is forced to her limits when she becomes the target of a gang of teenagers. After spying on the vulnerable woman as she showers, they break into her home, humiliate and assault her. Something inside this reclusive teacher snaps and the thirst for vengence takes over. Bloody and clad in lingerie, she mutilates her attackers using some rather interesting and gory methods.