What happens to Charlie when he is eleven years old is that he wants to send a valentine card to a girl called Harriet, who distinguishes herself not just by being pretty and attractive, but also because she acts differently towards Charlie compared to the other children at his school:
She never teases him like the other kids, and he does tricks for her... And Harriet always screeches and giggles, "Oh, lookit Charlie. Ain't he funny? Oh, ain't he silly?"
He decides therefore to give Harriet a locket that belongs to him. He asks his so-called friend, Hymie, to write a note to go with this locket that he carefully dictates to Hymie. However, it is clear that Hymie writes a rude, dirty and offensive note that upsets Harriet so much that her two brothers beat up Charlie and he ends up having to leave and go to another school. This event is significant, because it indicates Charlie's growing awareness of the way in which people who pretend to be friendly are actually incredibly cruel to him and make fun of him because of his low intelligence.