Scooby, Shaggy and Scrappy Doo are on their way to a Miss Grimwood's Finishing School for Girls where they have been hired as gym teachers. Once there, however, they find that it is actually a school for girl ghouls. The pupils include Sibella, the daughter of Count Dracula; Elsa Frankenteen, the daughter of Frankenteen Senior, Winnie, the daughter of a werewolf; Phantasma (usually called Phanty for short), the daughter of a phantom; and Tanis (which is a parody of an Egyptian city), the daughter of a mummy. Other residents of the school are Miss Grimwood, the headmistress, a floating white hand, who is the butler, and her pet dragon Matches (who dislikes Scooby at first, but later becomes friends, and has a strong liking for Scrappy).
Gym class soon starts, with the intent to train the girls for their upcoming volleyball match against the boys of the neighboring Calloway Military Academy (who have always beaten them). As an additional plot twist, Revolta, the self-styled Witch of the Web, and her minion, the Grim Creeper, plan to kidnap the girls and make them her slaves. The girls' fathers come for Open House, but as they leave, they warn Shaggy and Scooby not to let any harm come to their daughters. Despite being well-liked by all their students, Shaggy and Scooby have enough of this and run away when monsters such as an alien, the Creature from the Black Lagoon and Godzilla enroll their daughters at the school for the following year, but not before they, Scrappy, the girls, and the Calloway boys foil Revolta. As they leave, they see the girls and Matches wave them goodbye. Shaggy, Scooby, & Scrappy then give them a last werewolf howl before driving off.