Caillou is watching out the window because he wants to see the school bus when it comes. Daddy keeps calling him to do things, which annoys him because he might miss the bus. He does get to see it, though and it gets him to wishing that he could go to school. That evening, Sarah comes over with an invitation. Her school is having a little brother/sister day. She doesn't have one, so she wants to invite Caillou to come instead. Caillou's parents agree and the next day, Caillou is off to school. He wants to bring his dinosaur, but his Mommy says he doesn't need it. He'll have so much fun at school that it'll just get forgotten in his backpack. Caillou's Mommy drives Caillou and Sarah to school. There, Caillou thinks the school is very big. Sarah holds his hand as they go in. Caillou gets to see Sarah's classroom briefly, but then they have to go to the gym for assembly. Once there, Caillou wants to play, but Sarah tells him they have to sit and listen. As the principal drones on about "fun-filled, action-packed day," Caillou starts to get antsy. He has to use the bathroom. Later, Caillou and Sarah are back in the classroom, drawing on the blackboard. Normally they couldn't do this, but it's allowed since it's a special day. Then they have recess, during which Sarah comments that she likes school, but wishes they had more time outside. Caillou doesn't understand until the bell rings and Caillou realizes that recess seems very short. Back in class, Caillou enjoys painting. Then later, they have lunch and Caillou and Sarah decide to switch their lunches. On the way home that day, Caillou tells Mommy all about what he did in school and then goes to sleep in the back of the car.