Sounds like your school district runs a more cost effective operation than mine.
First - There is never a teacher at the elementary school down the street from me before 8:15. They leave before the buses do so they don't get held up on their drive home. By 3:30 (school's out at 3) the only car in the lot is the janitors. The High School is pretty much the same except for the coaches, who get extra pay for that after school work.
Second - Our teachers don't work all day. In the middle school/high school the day is 7 periods long; my friends who are teachers complain if they are scheduled to teach 4 periods a day.
Third - Every classroom has at least one aide. They do the things like collecting papers, hanging things on the bulletin boards, cover the coffee breaks, etc. If there are any "mainstreamed" kids in the class there are generally 2 aides.
Fourth - you clearly haven't mastered the art of having the kids grade each others papers. My children started public school in third grade (after starting out in a private school), and began this quaint practice immediately. The downside to the kids is that if your fellow student marks things wrong that are right, it's up to the student to get the teachers attention to make it right. The teachers don't review this grading process.
Finally - you need to get a clearer understanding of how much your workload will be reduced by group projects. If you have 25 students, and have them do math problems, english papers, or spelling tests as a group of 5, you'll only have 5 papers to grade instead of 25.
You may think I'm being facetious, but in my school district, which touts itself as a "world class school district" (and ranks high in the state for academic quality) this is the norm. Last I heard (a couple years ago) average teacher salaries were $65,000/year.
Maybe, maybe not. Please don't think that all the teachers in my district are in that early, they are not. My coming in that early is because I want things to go as smoothly as possible in the classroom. Therefore, I do my best to prepare, prepare, and then prepare.
Also, this was my first year to teach, and I had six different class to prep for each day. My number of preps for this year is down (4), and I have a little experience under my belt. However, I will still go in that early in the morning because I have been getting up that early to go to work for the past 20 years regardless of what position I have held.
Where is this? Sounds like the fictional school in 'Ed' where all I ever saw 'Miss Vessy' do is water plants, go out to lunch, and put books away.
Two aides/class? I had to cry and scream to get one parttime aide with 4 special ed kids along with several SEP kids and 16 reg. ed. kids.
Group projects don't reduce workload. Planning them so all students work and actually learn is an art.