"Alphabet For Homework" joke

One day when Jimmy was at school, the teacher told him that for his homework he had to write out the first three letters of the alphabet.
When he went home he was struggling so decided to ask his mum. His mum was in the kitchen cutting the salad when he asked her "Mum, what is the first letter of the alphabet?"
Just as he had finished asking this question his mum sliced her finger open and shouted "SHIT!!!"
Jimmy wrote this down and went outside to see his older brother.
He asked him "big brother, whet is the second letter of the alphabet?"
His brother was crouched on the floor talking to a drugged up teenager and jimmy heard him say "only if you give me some heroin!"
Jimmy wrote this down and went into the living room and saw his little sister watching superman.
"Sister, what is the third letter of the alphabet?"
His sisters eyes were fixed on the the TV and she ignored Jimmy. "Superman!!!" she shouted out in excitment.
The next day when Jimmy went into school the teacher asked him if he had done his homework.
Jimmy then shouted out "SHIT!!!" (the first letter of the alphabet.)
His teacher was very angry and shouted "right young man, you're going to the head teacher!"
and Jimmy replied by saying "only if you give me some heroin!" The teacher's face went red with anger and dragged Jimmy to the head teacher's office by his ear. When Jimmy and the teacher were in the head teacher's office the headteacher asked, "who do you think you, are young man?"
So Jimmy shouted "SUPERMAN!!!"