Scooby-Doo and the Ghoul School (1988)

Hey there, it's the ghoul school!

Scooby, Shaggy and Scrappy are on their way to a Miss Grimwood's Finishing School for Girls, where they've been hired as gym teachers. Once there, however, they find that not only is it actually an all-girl school of famous monsters' daughters but there's a villainess out to enslave the girls.