Teacher: "What is the outer part of a tree called?"
Pupil: "I don't know sir."
Teacher: "Bark, boy bark."
Pupil: "Woof-woof."
Teacher: "Give me a sentence starting with the letter 'I'".
Pupil: "I is-"
Teacher: "No, you must always say 'I am'."
Pupil: "Okay, 'I am the ninth letter of the alphabet'."