Dentist Visit

I was sitting in the waiting room for my first appointment with a new dentist. I noticed his DDS diploma on the wall, which bore his full name.
Suddenly, I remembered a tall, handsome, dark-haired boy with the same name had been in my high school class, some 30-odd years ago
Could he be the same guy that I had a secret crush on way back then? Upon seeing him, however, I quickly discarded any such thought. This balding, gray-haired man was way too old to have been my classmate.
After he examined my teeth, I asked him if he had attended Northmont high school.
“Yes. Yes, I did. I’m a thunderbolt,” he said gleaming with pride.
“When did you graduate?” I asked.
He answered, “in 1975. Why do you ask?”
“You were in my class!”, I exclaimed.
He looked at me closely, then, the ugly, old, bald, wrinkle-faced, fat, gray-haired, decrepit fool asked, “What did you teach?”