In the morning the father knocking at the door of his son and cries, "Come on, you have to get up now!"

"But I do not want to!" says the son and pulls the blanket over his head.

When his father reminds him again: "You've go to school!"

Says the son: "I'll give you three good reasons why I do not want. First I have no desire, second I do not like the school and third nobody likes me at school."

The father responds to his son: "And I can tell you three good reasons why you have to go to school first, it is your duty, second. you are 45 years old and third you are the teacher!"

Hans comes satisfied from school: "Today we have made explosives!"

"And what are you doing in school tomorrow?"

"Which school?"