Two boys and a teacher

Two boys were arguing when the teacher entered the room. The teacher asked the boys.
Teacher: Why are you arguing?
Boy: We found a ten dollar bill and decided to give it to whoever tells the biggest lie.
Teacher: Oh dear, you should be ashamed of yourselves. When I was your age, I didn't even know what a lie was.
Boys: Wow! You got it!
Then the boys gave ten dollars to the teacher.