>>> The problem isn't so much when teachers make mistakes -- it's how they react to them when they are pointed out.
I never had a problem with that. I used to run the school football teams. On one occasion, due to a mix-up over substitutions at half-time, a parent had to point out to me that our team only had 10 players on the pitch. I also edited the sports page of the school newsletter, so I made sure that the next issue carried the headline "Maths Teacher Can't Count!"
;-)