Penis on the blackboard

The teacher enters the classroom and sees a huge member drawn on the board. She asks the class:
– Who drew it?
After a short silence, Peter gets up:
– I drew.
– So, please come out of class.
Both leave, do not return for 10, 20 minutes … After half an hour, a satisfied Pēterītis enters the class and, pushing his pants forward, determines:
– I said – advertising has power.