I have mentioned several times before that I spent my last years before retirement as a technical trainer, teaching maintenance procedures and trouble-shooting techniques to service technicians in the office equipment industry. I don't think that I have ever mentioned my first experience as a teacher.
We had just moved to Alvin, Texas, and I was a junior in high school. I signed up for a class in Solid Geometry, and I think I was the only junior in the class; everyone else was a senior. Just before the start of the year, the math teacher suffered a mild stoke which had him out on sick leave for the semester.
Frank Leathers, the Alvin High School principal, took over the class, but quickly admitted that he really didn't have a head for math - he'd been an English major - and was in way over his head. The subject came easy to me - it was almost intuitive. There was one other student who "got it" as well, and he and I ended up teaching the class.
I prepared the lesson plans, wrote and graded the tests, and stood at the blackboard and lectured every day. Mr Leathers sat at the teacher's desk and tried to follow along.
Needless to say, I got an A in the class.