Son:
“I got expelled.” …..
…..
Dad:
“How?” …..
……
Son:
“I wrote 2 + 2 = 41 on the whiteboard.” …..
…..
Dad:
“That’s pretty dumb but-” …

Son:
“Then my teacher told me to go back up to the board…”

Dad:
“Ok?”
Son:
“And rub 1 out.”