During an inspection by Superintendent Chalmers, Principal Skinner lures Bart, Jimbo, Kearney, Dolph and Nelson into a utility basement with the promise of free mountain bikes and locks the door. Bart escapes through a ventilation shaft and takes Groundskeeper Willie's tractor for a joyride, crashing into Chalmers. Rather than giving him detention, Skinner instead expels Bart. After Bart is quickly expelled from a new private Christian school, Marge decides to homeschool Bart.
Meanwhile, Kent Brockman announces that Springfield's annual "Whacking Day" is approaching. Each year on May 10, the people of Springfield drive snakes to the center of town and beat them to death. The tradition appalls Lisa, who finds no support from any of the adults of the town, including Reverend Lovejoy who lies about Whacking Day being supported by the Bible. Barry White arrives to begin the festivities, but is disgusted and quickly leaves when he discovers what the holiday is about.
After Marge takes Bart on a fieldtrip to Fort Springfield, Bart discovers that the origins of Whacking Day, which supposedly involved Jebediah Springfield, is a lie because it conflicts with a major Revolutionary War battle he took part in, and suggests to Lisa that they lure the snakes to safety by playing music with a lot of bass and putting the stereo speakers to the ground. White, who just happens to have been walking by, agrees to help by singing "Can't Get Enough of Your Love, Babe", attracting hundreds of snakes into the house.
The pursuing crowd arrives, but they are soon turned around on the subject of Whacking Day by Bart's newfound knowledge. It turns out that the day was actually invented in 1924 as an excuse to beat up the Irish. Skinner is impressed with Bart's efforts and welcomes him back to the school, but then realizes in horror that the bullies are still in the utility basement. While the bullies are spending the time talking about their feelings, Skinner and Willie race to the school with the mountain bikes to avoid a potential lawsuit.