Peter was a clever boy. On his first day at school, he learned three words: I, You, and She. The teacher taught him how to make sentences with those words.
The teacher said, "I, I am your teacher." Then, pointing to a girl, "She, She is your classmate." Finally, "You, You are my student."
When Peter went home, his father asked him what he had learned. Peter repeated immediately, "I, I am your teacher." Then, pointing to his mother, "She, She is your classmate." And, "You, You are my student."
His father got angry and corrected him, "I, I am your father." Then, pointing to his wife, "She, She is your mother." And, "You, You are my son."
The next morning, the teacher asked Peter if he had learned the three words by heart. "Yes," he said proudly, "I, I am your father." Then, pointing to a girl, "She, She is your mother." And, "You, You are my son."