Casper's Scare School (2006) on Netflix

Plot summary

Kibosh, King of the Underworld, is unhappy that Casper would rather play with a human boy, Jimmy Bradley, than scare anyone, and that Casper has failed to scare enough humans. Casper can either enroll at Scare School or be banished to the Valley of Shadows. Alder and Dash, one headmaster with two heads, run the school, where students learn to frighten humans, the fleshies, so the creatures of the Underworld can hold their own against them. Casper's first three lessons end in detention. Two classmates become his friends: Ra, a mummy whose bandages come loose, and Mantha, a zombie girl whose limbs keep coming off. A pirate, Cappy, and his parrot Beaky ferry the students to the school. Thatch, a vampire bully, spies on Casper, looking for a way to ruin him.