Knock, knock. Who's there? Spell. Spell who? W-H-O.
Knock, knock. Who's there? Broken pencil. Broken pencil who? Never mind, it's pointless.
Why don't we write with broken pencils? Because it’s pointless.
Why did the student eat his homework? Because the teacher told him it was a piece of cake!
Why was the math book sad? Because it had too many problems.
What did the janitor say when he jumped out of the closet? Supplies!
Knock knock. Who's there? Pencil. Pencil who? Pencil me in for lunch tomorrow!