A childhood belief about teachers

When I was in second grade, I thought that a third grade teacher, Mr. Thomas, was actually another third grade teacher called Mr. Brock. I thought this because every time I passed Mr. Brock's class, I saw Mr. Thomas walking out of it. When Mr. Thomas turned out to be my teacher next year, I must've sounded pretty dumb saying that he looks like Mr. Brock. By the way, Mr. Brock is black and Mr. Thomas is white.