Keep in mind that in our school district, elementary school students need to be in by 8:40 while high school students need to be in by 7:50.
Our neighborhood is setup for walking. The elementary school is a six block walk, so most people walk their kids to school. My daughter didn't sleep past 7:00 for most of elementary school. Our experience was that elementary really could have started closer to 8:00.
I'm with you on all your other points. But, I think our experience was significantly different for elementary school.