I love childish jokes too.
Teacher: Didn't you hear me call you ?
Pupil: But you said not to answer you back !
Teacher: Why can't you ever answer any of my questions ?
Pupil: Well if I could there wouldn't be much point in me being here !
Teacher: I said to draw a cow eating some grass but you've only drawn the cow ?
Pupil: Yes, the cow ate all the grass !
Father: How were the exam questions ?
Son: Easy
Father: Then why look so unhappy ?
Son: The questions didn't give me any trouble, just the answers !
Father: Why did you get such a low score in that test ?
Son: Absence
Father: You were absent on the day of the test ?
Son: No but the boy who sits next to me was !