Then a significant majority of teachers are not "good", by your definition. Some simple arithmetic: given that teachers are excluded from that study if they wo

Then a significant majority of teachers are not "good", by your definition. Some simple arithmetic: given that teachers are excluded from that study if they work less than 35 hours, we discover at most (38.5-35)/(K-35) % of teachers work K hours/week. (This is based on the extreme case of x% of teachers working K hours, 1-x% working 35 hours.) So if 50 hours/week is "good", then at most 23% of teachers are good. As for your subjective opinions about "thankless", what evidence - if any - would cause you to change your belief?