Is it really? I don't know about your school, but with all of the required training, paperwork, etc. I know quite a few teachers that work some ridiculous hours grading. Personally I spend about 14 hours a day at work in the fall, but I do get paid a bit extra based on the amount of extra time I put in. This 9 months stuff though simply isn't true anymore. The expectation is that teachers spend at least 4 of those weeks doing workshops and training opportunities that mostly don't involve pay to do so. If you're fortunate the district might pay for the training.
Also, 64k is plain and simple not much I'm guessing cost of living wise there. Personally I started in another state at 31k with a Bachelor's Degree just nine years ago. My colleagues in other fields jumped in at similar degrees at 55k+. I had probably 60 more credit hours when I graduated than them too! At this point I'm paid about as well as I could expect at 50k where I'm at. That's with significant extra duty pay amounts built-in, and I feel bad for the teachers without that because they're not being paid well enough.
Oh, and the fact you don't see the homework doesn't mean teachers have nothing to grade. Many of those teachers are teaching seven periods a day with the maximum number of students in each class. Figure roughly 210 students a day with a grade expected from many of them on every assignment. Even if you're just putting a checkmark and marking it in the computer at a rate of .5 minutes per assignment you're talking 105 minutes of work. You figure you get home at five or so, fix dinner, eat, you're up to seven. Let's say you have kids and have to take care of them, some of them don't start grading till nine, and don't finish till nearly eleven at that rate.
Just because you don't see your childs' teachers working does not mean they do nothing. You probably get to leave your work at work. Must be nice?