Nice ones..

1)Teacher : "Now, children, if I saw a man beating a donkey and stopped him, what virtue would I be showing?"
Student : "Brotherly love".

2)Tom : "How should I convey the news to my father that I've failed?"
David: "You just send a telegram: Result declared, past year's performance repeated".

3)Teacher : "What do you call a person who keeps on talking when people are no longer interested?"
Pupil : "A teacher".