Bart swaps papers with class nerd Martin during an intelligence test at school. When the school psychologist compiles the test results, he believes the switch and refers Bart to the Enriched Learning Center for Gifted Children. The new school's laid-back liberal ethos suits Bart just fine - until he's asked to show evidence of his neglected genius.
The episode begins as the Simpson family plays Scrabble, in the living room, in an effort to build Bart’s vocabulary for his aptitude test tomorrow at school. Bart, however, is un-enjoyed to the game, so he ends the game when he cheats and makes up an imaginary word, “Kwyjibo,”. Before he leaves, Homer roughly gruffs on him for cheating and forces him to define "Kwyjibo". Bart eventually defines it as, “A big, dumb, balding, North American ape with no chin.” Marge adds minor detail to the definition of "Kwyjibo", with "and a short temper". This causes Homer to become instantly angered and chases Bart out of the room, as Bart replies "Uh-oh. Kwyjibo on the loose."
The next day before class, in the schoolyard, Bart is spray-painting graffiti that defames Principal Skinner on the school building. Principal Skinner is watching the kids on the playground. Martin Prince, the school genius, tattles about the graffiti. Milhouse, one of Bart's friends, sees Martin informing Skinner and warns Bart. Skinner arrives, where Bart, Milhouse, and two more children are feigning their involvement. He then checks each of their hands, but Bart's hands is caught "red-handed". Skinner orders Bart to see him after school.
As the children file into class, Martin encounters Bart in the classroom, explaining that he feels apologetic for Bart and merely was attempting to prevent the desecration of the school, but Bart grudgefully rebuffs Martin, replying "Eat my shorts". Mrs. Krabappel hands out aptitude tests to everyone. When she instructs the class on taking the timed intelligence test, Martin raises his hand, and reminds her that Bart is supposed to face the window during any test so he can’t cheat. A grumbling Bart turns his desk to face the window and the test begins. In an attempt to figure out a lengthy math word problem, Bart tries to quietly read the problem so he can solve it. Mrs. Krabappel reminds him for visualization instead. The visualization turns into a daydream and when Bart finally comes back to reality, Martin announces that he has finished his test already. Mrs. Krabappel sends Martin outside to read a book, during the remainder of the testing period. While Bart is still taking his test, he looks out the window to see a smug Martin sticking his tongue out at him. In retaliation, Bart makes faces back at Martin; Mrs. Krabappel spots Bart making faces and looks out the window to see what Bart is looking at. While her back is turned, Bart, who is seated at the front of the class, reaches over to Mrs. Krabappel’s desk and steals Martin’s test, replaces Martin’s name with his own and then puts the test back on her desk. Bart then quickly fills out random answers on his own test and then writes Martin’s name at the top and turns it in.
Later, after school, Marge and Homer are called to Principal Skinner’s office for a meeting about Bart’s behavior at school.
Skinner informs Marge and Homer about Bart’s graffiti from earlier that morning. As he reaches for Bart’s rather extensive permanent record, and is about to suggest something along the lines of expulsion for Bart, his secretary buzzes in and says that Dr. J. Loren Pyror, the school psychiatrist is waiting to see him. Dr. Pryor walks in on the meeting, and surprises everyone when he tells them that Bart is a “gifted child,” and according to the aptitude test from earlier, Bart has an I.Q. of 216. Dr. Pryor suggests that Bart’s history of bad behavior stems from a lack of interest in his school work, due to the fact that it is too easy for him. Skinner wants Bart retested, but when Dr. Pryor suggests moving Bart to a school for "gifted children" Skinner jumps on board with the idea, and Bart quickly agrees when he hears that the school doesn’t have much structure and that you get to make your own rules. Dr. Pryor hands Bart some paperwork for the “gifted children” school, and he, Homer and Marge leave the meeting stunned.
The next morning at the breakfast table, Marge and Homer hover around their new genius child and Homer tells Lisa to start eating what Bart eats for breakfast, so she can become a genius too. However, Lisa is not fooled by Bart and knows that he is still just a dimwit. After breakfast, Homer takes Bart to the “Enriched Learning Center for Gifted Children.” Once inside the school they find Bart’s class, and after peeking in, they see that all the boys are wearing ties. So Homer gives Bart the tie he is wearing, and he gives Bart a little pep talk about his first day at the new school and shoves him in the classroom door. Once inside the class, Ms. Melon, the teacher introduces herself and the new classmates to Bart and shows him around the classroom. She tells Bart about the independent learning and that the only rule is for him to make his own rules. Class begins with a debate on the topic of free will and the paradoxes that it creates; Bart struggles to understand the discussion. Later at lunch, Bart’s classmates realize that Bart isn’t really that smart when he accepts their ridiculously uneven trade offers. (Ex: 1000 Pico liters of milk for 4 gills worth. A gill is much, much larger than a Pico liter.) A dejected Bart walks away from the lunch table as the other kids laugh at him.
After school, Bart relaxes in his room, when Homer walks in to see about Bart’s first day at the new school. Homer suggests they all go out for frosty chocolate milkshakes and Bart agrees. Just then Marge walks by, and tells Homer and Bart that she bought tickets to the opera in an effort to try to help nurture Bart’s brain. Later during the opera, a bored and impatient Homer and Bart goof off and cut each other up, even though they are continually shushed by an upset Marge. Cut to the next day at school where Bart feels even more stupid and left out when he can’t understand a calculus problem on the chalkboard. Later, as a sad Bart walks home from school, he passes by the playground of his old school, where Richard, Lewis, and Milhouse are shooting marbles. When Bart greets them and tries to talk to them, they treat him like a nerd, call him names and tell him to get lost. Cut to later at dinner, as a depressed Bart eats, Marge reminds everyone that they can’t be late for the film festival that she bought tickets for, as another way to nurture Bart’s brain. Bart is reluctant to go to the festival and Homer tells him they don’t have to. Just as Bart is about to tell Homer what is on his mind and confess about the false I.Q. test, Homer insists on going outside to play catch. After playing catch, Bart sees how much being a genius means to Homer and decides not to confess about what he has done, out of fear of disappointing him.
The next day at the “gifted children” school, while performing a chemistry experiment, Bart accidentally causes an explosion, which results in green goo everywhere. Cut to Dr. Pryor’s office, where a green stained Bart meets with Dr. Pryor. They discuss the reasoning behind his recent failings at the new school, and Dr. Pryor thinks that once again Bart isn’t being challenged enough, while Bart suggests that he just go back to Springfield Elementary. When Dr. Pryor wants to know why, Bart makes up an excuse and tells Dr. Pryor he would like to go undercover and study regular kids and their school environment, “to see what makes ‘em tick.” Dr. Pryor agrees and tells Bart to write up a proposal to present to Principal Skinner while he goes to talk to him. Bart struggles to write a proposal and instead changes his mind and writes his confession. When Dr. Pryor comes back in the office and reads Bart’s confession he suddenly realizes that Bart was never a genius to begin with. Later at home, a still green-stained Bart greets his parents and Homer offers to give Bart a turpentine bath to wash off the green. Out in the backyard, as Homer gives Bart a bath, Bart confesses about cheating on the aptitude test and tells Homer that he loves him and that he has enjoyed the extra attention from being a “genius.” He tells Homer that he doesn’t think something that has brought them closer than they ever were before could be bad, but Homer doesn’t see it Bart’s way, and he chases Bart out of the tub, trying to choke him. Bart is too quick for Homer and runs into his bedroom and locks the door. An angry Homer pounds on Bart’s door, and tries to coax him to come out, while Bart taunts him from inside his room. Everything is back to normal in the Simpson home.
This episode marked the first time that the opening sequence was used, which was different from the second season opening which would be later introduced in "Bart Gets an "F"".
The Simpsons logo is in a darker blue sky with a few clouds.
The school is white instead of orange.
The background that is used when Bart is skating out of school is crudely drawn.
At the power plant, there is a bald man eating a sandwich with tongs. (Instead of Mr. Burns and Smithers)
The walls of the supermarket are red.
Maggie's hands are on her hips.
Lisa has a much higher-pitched saxophone solo and a purple and blue saxophone.
When Homer throws the rod out of the car, it bounces near Moe's Tavern.
When Bart is skating through town, he steals a bus sign from a group of waiting people. The people run and chase the bus when it passes by them.
Marge and Maggie ride home in a red sedan.
There is a sequence with Lisa riding home on her bike with a stack of books and her saxophone. (This was later replaced with the whip across the Springfield citizens.) Also, Lisa gets home first, so Homer only has to dodge Marge after getting out of the car.