Linguistic humor, School days

Source: Via Tsan-Kuang Lee.

Morphology

Mother: Why on earth did you swallow the money I gave you?
Junior: You said it was my lunch money.

Lexical ambiguity

Teacher: In this box, I have a 10-foot snake.
Sammy: You can't fool me, Teacher … snakes don't have feet.

Structural ambiguity

Teacher: How can you prevent diseases caused by biting insects?
Jose: Don't bite any.

Usage

Teacher: Ellen, give me a sentence starting with "I".
Ellen: I is …
Teacher: No, Ellen. Always say, "I am."
Ellen: All right. "I am the ninth letter of the alphabet."