Maths homework...

A little boy was doing his maths homework.
He said to himself, "Two plus five, the son of a bitch is seven.

Three plus six, the son of a bitch is nine..."
His mother heard what he was saying and gasped, "What are you doing?"

The little boy answered, "I'm doing my maths homework, Mom."
"And this is how your teacher taught you to do it?" the mother asked.
"Yes," he answered.

Infuriated, the mother asked the teacher the next day, "What are you
teaching my son in maths?"

The teacher replied, "Right now, we are learning addition."
The mother asked, "And are you teaching them to say two plus two, the son
of a bitch is four?"

After the teacher stopped laughing, she answered,

"What I taught them was, two plus two, THE SUM OF WHICH, is four."