Principal Skinner prepares for Superintendant Chalmers's surpirse inspection by locking Bart, Jimbo, Dolph, Kearney, and Nelson in the school's basement. Bart escapes and takes Groundkeeper Willie's tractor for a ride. Skinner expels Bart after he mows into Chalmers's backside.

Lisa is horrified by the approaching holiday, "Whacking Day," in which town residents beat snakes to death with clubs. Marge decides to teach Bart a herself, turning the garage into a makeshift classroom. Bart reads Johnny Tremain and willingly accompanies Marge to Olde Springfield Towne.

Whacking Day arrives and Lisa begs Homer not to participate, but he refuses to listen. With the help of the bass voice of Barry White, Bart and Lisa lure all the snakes in town into their house. An unruly mob arrives, so Bart reveals that his research has unearthed the holiday's original purpose: it was concocted as an excuse to beat up the Irish. To reward Bart for his studies, Skinner allows Bart to return to school.