That was the year when we were taught of the speed of light and the specific question might have been at the end of the same chapter in the text book.
Somehow I had a vague feeling that the effect of turning on the switch should not reach the light instantly.

It was much later, that I found out how it was related to the absolute speed of information that is available in current theory.
Note, that I hadn't used the internet as much back then and it was much later, that I started diving into Wikipedia.

On the other hand, teachers are supposed to be university graduates themselves, so considering that I had the answer to that question by 12th, I would expect the teacher to at least be able to correctly answer that.