There are some good points to what you say.
However, in MY name-droping 2nd-hand experience, my mother was a teacher all her life except for a few years trying to make it in real estate. She taught all levels in her career, but the dominant theme was emotionally disturbed - and she became "teacher-in-charge" at the special (albeit small) attached school for ED teenagers for 15 years.
The worst part (as far as "hours") for my mom was the extra time at night actually taken for checking papers, etc. Otherwise, it was basically strictly her specified duties DURING school hours. This was certainly true of all the other "plain" teachers. I also knew her underling teachers pretty well as well as my own HS teachers, because my mom's ED school was attached to my HS administratively.
And let's not forget not every teacher is in HS. There are ES and MS that hardly do anything truly extracurricular.
And MANY did NOT "work all Summer". My mom didn't, and neither did any teacher she worked with.
At the rate schools are performing, I wouldn't say teachers are underpaid. My mother was a great teacher (she even has a boy from her last ED MS who visits her still 5 years after she retired), but far too many aren't. Of course, it's not all teachers' faults, but they're part of the cycle.
When that changes, maybe we'll talk about higher pay. My mother, incidentally, would agree.
"There are ES and MS that hardly do anything truly extracurricular. "
And there are a lot WHO do too.