Ok, schoolsc are typically some variation of 8-3, which is 7 hours. I have no idea where you're getting 12 hours from other than some crazy extreme outlier.
During that 7 hours, you think they just sit in a room, and get handed shit after shit? That's not even close to reality. That "massive" 7 hours is about 4 hours broken up into 45-1 hour increments after you have lunch/recess for an hour, a second or third recess that's 30-1 hour, art class, music class, gym, ect.
Beyond that, I have no idea how you think they should learn anything without sitting and practicing. I'm not sure if you're aware, but when a lot of states went to in hime learning during covid, the kids did fucking horrible.
You don't want 25 kids in a class with 3 teachers? Pay more taxes to hire more people to be in the class. You don't want higher taxes? Well your math doesn't math. If you think teachers only work between their contract hours, you're on fucking crack. All that decorative shit in their room? That's out of pocket not reimbursed shit they bought. All the little snacks your kid gets is out of pocket, not reimbursed. Most teachers skip their lunch and they don't get a penny of overtime.
How would you feel if you had to buy nearly everything at you job you used, turn had to work 50 hours a week to get your job done right to be paid for 40 hours. Getting paid on breaks? Yeah, you're paying yourself. Every check has an amount withheld so you can pay yourself over breaks, holidays, and summer. It's not "free money" you're paid.
Then you have parents like yourself that have zero clue how anything works, how to even deal with working in a class with 25 kids. But somehow you have all the answers and are an expert? Sure, whatever you say.