It looks like Oskar's buddy Klepp has come back to visit him. Klepp loves to draw up detailed schedules mapping out how he plans on spending every second of every day.
This causes Oskar to reminisce about the first time he was ever introduced to the world of schedules. He was just a young boy, strapped to a woolen harness that connected him to a bunch of other kids in his kindergarten class.
One day, he notices that another kid was punching his cousin, Stephan Bronski, in the face and calling him a Polack. It turns out that not everyone's cool with Polish people in Danzig. They were a persecuted minority.
Stephan eventually has to leave the kindergarten, and Oskar leaves with him.
Oskar's sent to a new school. But the teacher in this school is very strict and used to having things her own way.
She likes to have school days go according to a strict schedule, and has absolutely no time for Oskar's tin drum. But you can guess what happens when she gets out her whipping cane and tries to punish Oskar for holding onto it.
Yep. She gets the scream. And since she's wearing glasses, Oskar's scream almost blinds her by shattering her lenses.
She declares Oskar to be a terrible little boy. But hey, Oskar gets himself out of the school, which is all he wanted to begin with.
In case you haven't noticed yet, Oskar likes to do things on his terms. So that's a big no to any kind of formal schooling.
The only evidence Oskar has of his one (and only) day at school is a photograph taken after shattering the teacher's glasses. It appropriately bears the words, My First Day at School.