Ah yes, the "you're a teacher, you don't work that hard! And you have soooo much time off!" line. I get that one a few times every week and at the beginning it was bugging me, but at some point, it just gets tiresome
I know older colleagues who just don't seem to care as much anymore and don't come close to 48 hours a week because they don't spend a lot of planning anymore. At the same time, the young teachers who've just graduated from university are buried in work ... my first year was brutal in that regard.
I kind of like Lockes argument of working "a lot" instead of "hard", I think that's a fair statement. I will say though that I worked in an office a few years ago and I can honestly say that 3 hours of teaching can be much harder than 10 hours of office work.