Help, I Shrunk My Parents

Felix's school is haunted again, only this time it's not the benevolent spirit of school founder Otto Leonhard and the nuisance he caused, but the hated and long-since dead Director Hulda Stingbeard. When she manages to return to real life she almost defeats Otto Leonhard, manages to shrink Dr. Schmitt-Gössenwein and Felix' parents, and takes over the school. (TMDb)