I think education is the 2nd most important thing in a child's life. (The first being a loving family). A person's education sets them up for the rest of their life, and opens doors and opportunities that just simply can be gotten no other way. The foundation of a person's education is what the rest of their life is built off of.
What's more... I've come to believe that more than any other area of school until college, that early childhood education is THE most important arena. That's were love of learning, and the skills to go about learning, are laid to begin with. An adult can always go to community college, do fantastic, a state or private school, and ivy for higher ed on their own merits even out of the crummiest highschool... but if their ability to learn is killed in elementary, they're sunk more often than not.
THAT SAID
Here... an 8 hour day killed my son's love of learning.
Here... the entire year's curriculum was less than was covered in 1 month of preschool 3 days a week, 3 hours a day.
Here... the ridiculously long day (imho) ruined our son's time at home / outside of home, because he was EXHAUSTED. School was from 8-4. That meant up at 7 and home at 5. Morning madness, exhausting long and boring day, home just in time to melt down, eat, bathe, and repeat. And then the weekends had 20 pages of "homework" that took 10 hours to complete (fortunately after a month, our teacher gave us a pass, as he already could do the end of year homework. It was the boooooooooringness of them that just prompted meltdown after meltdown after meltdown.
It was TERRIBLE.
The day was FAR to long. There was nowhere NEAR enough playtime (30 minutes of recess). Lunch was at 10 in the morning, so the kids were CRASHING (even the non hypoglycemic ones) by early afternoon, and a complete mess by pickup.
TERRIBLE.
I wasn't happy with our district where we were livings option EITHER way. Half day was 2 hours, full day was 8. Worst of both worlds. He'd been doing 4-5 hour a day in preschool and had thrived and been bursting with excitment. We had enough time at home for a rich and varied home life. Once full day K started, all of that was out the window.