We're on the Road to D'ohwhere is the eleventh episode of Season 17.
When Bart finds the key to the school's steam tunnels and ruins the school with steam, Principal Skinner sends him to a camp in Oregon, but when Homer discovers Bart is on the no fly list, he has to drive him there; while they are gone, Marge and Lisa have a yard sale, only to discover that the big seller is Homer's expired pain pills. Marge is then arrested by Chief Wiggum and taken into custody. 
When Bart finds Principal Skinner's key to the steam tunnels while Skinner admires his new car, Bart and Milhouse fool around in the tunnels and open a steam valve, releasing a massive steam jet that explodes the school heaters, causes Groundskeeper Willie to burn his tongue when he tries to get a drink, rusts the band's instruments, causes frogs for dissection to come alive and attack the students, and generally rots the entire school. Skinner proposes that Bart be sent off to Upward Bound behavioral modification camp. Meanwhile, Moe announces that all of his frequent barflies will be going to Las Vegas, courtesy of him. Homer takes Bart to the airport to send him to the camp in northwest Oregon (preferably flying to Portland). But then he discovers that due to bad behavior on previous flights Bart had been placed on the no-flight list and needs to be driven to the camp, thus excluding him from Moe's Vegas trip. After driving to a roadside diner, Bart escapes, and Homer nearly drives off a cliff.
Meanwhile, Marge and Lisa have a yard sale. It is a total flop until Otto discovers that Marge is also selling the family's expired prescription drugs. Marge makes lots of money selling prescription drugs and with a high price; later Chief Wiggum arrests Marge and incarcerates her.
The next scene shows Bart tied to his seat with chains and duct tape to his seat. He complains to Homer that he enjoys seeing his own son suffer. Homer then tells Bart that talking time is over and silences Bart by putting tape over his mouth. Bart mumbles sadly into his gag. Homer gets Bart to the camp, but, after a moral dilemma, he plans to pick up Bart and take him to Las Vegas with him. In Vegas, Homer gets in a fight with a pit boss, loses track of Bart, and is thrown in Nevada State Prison. The final scene depicts Lisa receiving phone messages from both Marge and Homer, asking for bail money. She sighs, telling Maggie that she will look for employment the next day.