Seriously...
http://www.theatlantic.com/national/archive/2011/12/what-americans-keep-ignoring-about-finlands-school-success/250564/
Fundamentally, education is a social (and socialization) process. It has to come from the community. Middle-class teachers commuting to poor neighborhoods will rarely bridge the cultural gap needed to form a successful connection between teacher and student.
Beyond that, metrics get in the way of the intangibles that represent what really matters about learning. Kids these days are super-stressed and need down-time that isn't tied to a performance metric.
Eliminate screen time K-8. They get enough (too much) of it at home. There is zero competitive advantage in having a nation of kids that can use a mouse and click on icons all day. It's the most basic of skills to learn- no one is 'left behind' by an absence of screen time.
Double the time spent on physical education, with a focus on getting *outdoors*. Get some vitamin D and fresh air.
Bring back music and arts programs. So many intangible benefits- de-stressors, creative outlets, social engagement, neural development, etc, etc.
I spent hundreds of hours in band rehearsals. When I wasn't in rehearsal I ran cross-country. I paid a small amount of attention to homework and graduated first in my high-school class and then first in my engineering class. If I'd been educated under some standardized test regime I would have missed out on some of the most educational social encounters of my life. Fundamentally, I was successful because I felt I was part of a community that cared about success. Also, I was taught by teachers I could relate to.
FWIW I went to public school. Private schools were relatively rare, growing up. There was the sense that if you had to go to private school it was because you were struggling in the public system- a weak student who needed more 1:1 time. Times have certainly changed...