Wish I could pick just one, but in all fairness could not the question immediately invoked the two following scenarios..

Mary N. Crawford, shown sitting next to blackboard

Sorry this has to be a tie there are two - both from the same school. Went to one of those junior high schools for "gifted" students. When I attended it was the first year that the school was opened so a lot of "unconventional" things were going on.
There was an english teacher who apparently did not take great pains to grade or mark any of the assignments that she gave out, and in fact even tests came back with grades that made no sense and in some cases were not in line with the questions or the answers. A few students complained and got no where with it so - a group of students decided that on the mid term they would settle this once and for all. The mid- term was given and these students in the essay part of the test instead of answering the questions, all wrote...extended versions of mary had a little lamb....don't get too sentimental though extended in this case just means re-writing it over and over to fill up a certain space(or words requirement). Several students did this....ALL of them got 90 or better on the exam and that question was marked correct.....these students then took the exams to the principal as proof and that teacher was out of the building by the end of the day.

The other teacher - was not so much bad as she was ill-equipped to deal with a class full of inner city, gifted students. She too was an english teacher and her classes usually were pretty much out of order completely, Students carried on conversations, were rude and disrespectful and on several occasions there were spitballs thrown at her and throughout the whole room. It was on any given day just short of bedlam. One day however it just got way out of hand....i can't point to anything specifically different about that day it was about as out of control as the rest of the days were. This day however was different in that the teacher was at the board, writing out something about diagramming sentences and one of the "rowdy" students threw a massive spit ball at the teacher missed her and hit the blackboard right in front of her...She never turned around, just stood there. For a minute the room erupted into laughter but then after noticing she wasn't moving it got real quiet....and then....came the realization that, she was standing there back to the classroom frozen...and urinating on herself....which that got laughs for a minute and then some of the students got upset and one finally ran to the main office to get someone to come to the classroom....EMT's were called - teacher was taken out in stretcher...and as far as I know we were told that she had some kind of nervous breakdown. Never heard anything more about her after that. I always felt that she would have probably done much better in a classroom out in the midwest somewhere....