I'm a 6th year English teacher. During the school year, I work 50+ hour weeks. Rounding down, that is 1,850 hours in the 37 week and of school. That does not account for planning or continued training that I seek out absolutely pay for out of my own pocket and time outside of the school year. 

So, really, many teachers (most, in my experience) work as much, if not more than, your expectation, and do it in fewer weeks than you posit others do.