A teacher notices that Little Johnny at the back of the class is squirming around, scratching his crotch, and not paying attention. She goes back to find out what's up.
He's quite embarrassed and whispers that he had just recently been circumcised and he's quite itchy.
The teacher has him go down to the principal's office, to phone his mom, and ask her what he should do about it.
He does this and returns to the class, sits down in his seat and suddenly, there's a general commotion at the back of the room. Back down she goes, only to find him sitting at his desk with his penis hanging out.
"I thought I told you to call your mom," she says.
"I did," he says. "And she told me that if I could stick it out till noon, she'd come and pick me up from school."