"Know I know my ABC's..." joke

There was a little kid who needed to learn the ABC's for homework. He went to his big sister who was talking on the phone. "
What's the first letter of the alphabet?"
"
Shutup!"
Next he went to his older brother who was in the bathroom. "
What's the second letter of the alphabet?"
"
Down the toliet, in the toliet!"
Next he went to his other brother, who was watching Batman. "
What's the third letter of the alphabet?"
"
Nah-nah-nah-nah-nah-nah-nah-nah Batman!"
The next day, his teacher asked him what the first letter of the alphabet was. "
Shutup!"
The teacher asked him if he knew where he was going to go if he kept acting like this. "
Down the toliet, in the toliet!"
The teacher took him to the principal and he asked him what his name was. Do you know what he said?
"
Nah-nah-nah-nah-nah-nah-nah-nah Batman!"