Wednesday and Pugsley return home from school as Gomez performs his Latin Hour for Morticia and Fester. The children are reluctant to discuss their school day, but finally explain that the principal threatened to expel them because they showed their classmates how to shoot dynamite caps at recess. Unfortunately, one of them blew up the teeter-totter. Morticia and Gomez discuss the situation privately and Morticia is worried that the principal is depriving their children of their right to express themselves. She wants to transfer Wednesday and Pugsley to a private school and tells Gomez that the former truant officer and political candidate, Sam Hilliard, is now running the Mockridge Private School.
At Mockridge, the school secretary warns Hilliard that they're having trouble paying their bills. The Addamses arrive and Hilliard tries unsuccessfully to slip out the back. He remembers Wednesday and Pugsley all too well and doesn't want them at Mockridge. When Hilliard claims that he doesn't have any openings, Gomez offers him $10,000 and the headmaster reluctantly accepts. He breaks into tears and the couple figures that he's weeping for joy. Thing pops up to pat Hilliard consolingly on the shoulder, and the headmaster realizes that he's getting him as well.
Back at home, the Addamses test Fester's cannon before they donate it to the school for jousting and target practicing. Wednesday and Pugsley come home early from their first day at Mockridge and explain that the teacher was so touched by their displays at Pet Day that she sent them home early. They give their parents a note from Hilliard and go off to borrow Grandmama's alligator for the next pet day. The couple is shocked to learn that Hilliard is expelling the children despite the $10,000. Morticia calls the headmaster and he tells her that their children would be a menace to any school. The couple figures that the Board of Regents is pressuring Hilliard to go against his personal wishes and decide to buy Mockridge and run it in the Addams
Once they've made the purchase, Gomez renames the place Addams Hall and appoints Fester the Dean of Demolition, Dynamite, and Electronics. Sam reluctantly comes to see them, admitting that the Board of Regents sent him, and the Addamses explain that they're now the board of regents. They want him to stay on as headmaster and show him their new teaching aids: kinetoscopes and gramophones. Gomez assures Hilliard that they plan to introduce new classes like head-shrinking, taxidermy, and Dynamite 1 and 2. Grandmama will be providing baked mongoose for the home economics class. Thing will serve as the new attendance monitor, and Cousin Itt will be teaching animal husbandry so they can provide their own sheepskins. Hilliard says that he's quitting and runs out, and Fester offers to become the new headmaster. Gomez wisely ignores him and Morticia tells her husband that there's only one man for the job: Gomez.
Gomez soon installs himself at Mockridge and challenges the rival school to jousting. Things are going smoothly and absenteeism is at an all-time low. Fester is conducting the demolitions finals and Cousin Itt is performing speech therapy for dolphins. The Women's Club arrives and the head of the committee, Mrs. Bennet, informs the Addamses that they're less than thrilled to hear that their children are learning mine-laying and do-it-yourself dentistry. She presents a letter from all of the parents threatening to withdrawal their children if Hilliard isn't reinstated along with the original curriculum. Once the women leaves, Gomez begins to doubt his plan and Morticia suggests that they go home and reconsider the matter.
At home, the Addamses make their decision and send Lurch to drag Hilliard in. They tell the headmaster that due to the parents' loyalty, they've decided to reinstate Hilliard. They've donated enough money to keep Mockridge solvent forever, and agree to let Hilliard have complete control of the school. However, there's one catch, they want Fester to stay on as Deans of Demolition. Hilliard isn't so sure, but the Addamses assure him that Fester is working on a long-term explosives project and won't be available for several years. The headmaster eagerly agrees just as Fester blasts his way through the ceiling, explaining that it is going to take a while for him to get the explosives to blow up instead of down.
Later, the family is practicing music in the parlor when Wednesday and Pugsley complain that Mockridge is no fun now that Hilliard is back in charge. They want to go back to public school and Morticia agrees, but insists that they keep up their home studies with Fester and Grandmama. Gomez doesn't want to give up teaching now that it's in his blood, and calls his financier. He's disappointed to learn that they can't buy Harvard as a birthday present for Morticia, but tells the man to keep checking other universities.