Mistaken Identity

A guy goes to the supermarket and notices an attractive blond woman waving at him. She says "hello".

He's rather taken aback because he can't place where he knows her from. So he says, "Do you know me"?

To which she replies, "I think you're the father of one of my kids"

Now his mind travels back to the only time he has ever been unfaithful to his wife and says, "My God, are you the stripper from my bachelor party that I made love to on the pool table with all my friends watching while your partner whipped my backside with wet celery"?

She looks into his eyes and says calmly, "No, I'm your son's teacher".