Mrs. Smith, as you say, quite true. However there are many, many who do the absolute minimum. In my day, we would "exchange" exams and score them, pass them forward to the teacher. A few has us score tests in their study hall. One English teacher did not change her ciriculum over THREE GENERATIONS of STUDENTS! And she wasn't the worst, only the most anoying. She tought Shakespear without also giving us the meanings and useage of words AT THE TIME they were written, how people viewed things like ghosts/spirits and the like so much of it made no sense whatever.
At the same time, in the same school, there are dedicated EDUCATORS out there who damned near put in an hour at home and on weekends for each hour they spend in a classroom. Who make it easy to learn by making the clasroom experience a positive one. Unfortunately, they are the minority. The contracts that the districts have with the "union" make it near impossible to replace the bad and lazy once tenure is aquired.