Postcards from the Wedge
The Simpsons Season 21 Episode 14 (03/14/10)
When Bart misses an assignment and fails to intercept a letter that's being sent home, Bart gets the homework piled on him at school. Homer and Marge disagree on the amount of homework Bart should have to do, and Bart uses their different positions to get out of all homework. Eventually, the pressure drives Homer and Marge apart, until they each imagine life without each other and soon they make up.
Meanwhile, Bart and Milhouse pull a prank on Skinner and end up retreating in the abandoned Springfield Subway. When they activate an old car, it nearly collapses the school. When they were the school can't take another "quake," they go to run the line. However, Bart isn't getting his rush without getting in trouble with his parents anymore, so he decides to alert them to the plot. Homer ends up stopping him, but not before significant damage is done to the school, which collapses after a flagpole hits it. Grounded.