Phew, I've been reading education blogs all day and finally understand the new assignment process in SFUSD. (Which I have just managed to sidestep by getting Matilda into the new daycare at Grattan.)
Here's the thing: I think they got it right. Or at least it's a huge improvement on the previous Diversity Index, which was a massive exercise in bad faith and alienation.
Basically the lottery for school assignment was weighted by the Diversity Index which tried to capture racial differences without using race as a basis. The goal was to give more opportunities for poor families in poor neighborhoods to get into good schools (good idea) but wound up penalizing all the middle class white people (bad idea, white flight etc.)
Anyway, the new system is much more straightforward, and yet does a better job of creating that equity. In short, it identified the lowest scoring neighborhoods in the system and gave kids from those schools first dibs on the school system.
They could go to a low scoring local school or have a strong chance to get into an elite school crosstown. However, it also kept a strong local residential component that allowed people a chance to build their local school up.
There have been many turnarounds at SF schools, and largely because elementary schools can get big community involvement to improve the library, add technological infrastructure, create new arts programs, etc.
Another big huge draw for local schools have been language immersion programs. There was a failed school on Haight Street which got rebooted as a language immersion school and looks like it's going to take off in popularity.
Anyway, you always here about either (a) how all public schools are going down the crapper; or (b) how Some Amazing Educator comes in to turn around the school. But you can often grind out an improvement through smart, incremental changes.