I've known a number of teachers. Even dated one once... Not a one of them worked an "8 hour work day." Depending on the classes taught, they usually spent their lunch hour working while eating, were at the school an hour before classes started (7:30am), were usually there for at least an hour after class (4:00pm), and would often spend 4 to 6 hours a night working, either grading papers or planning classes.
I've also worked as an instructor (I never referred to myself as a "teacher." I taught adults how to design and run computer networks), and it required a tremendous amount of after hours work.
Mark
Gosh, I don’t know HOW I do it!! (homeschool my kids)