His mother asks him: "What's wrong honey? You look so sad."
The boy looks up at his mother and tells her: "Today, at school, I was punished for something I didn't do."
The mother, enraged, picks up the phone and dials the school. The secretary answers, asking what the mother's name was and what her child's name was.
The mother says: "Yes, my son came home today and told me that his teacher punished him for something that he didn't do."
The secretary proceeds to ask what the child was punished for.
The mother asks her son: "What is it that you didn't do, honey?"
"My homework."