I have a lot of writer friends who homeschool. And have many other friends with kids in private school. We're fortunate to be in a good public school district where our needs are being met. But I'm fascinated by all the options and the reasons why people chose the schools they choose. Especially in SF, for which it's competitive to get into the public school of your choice.
There's a new alternative school that opened up in San Francisco called the Schoolhouse. I haven't done much research on it (though it was profiled in the Wall Street Journal). This looks like a mix between private school and co-op - where you pay something like $7-9,000 a year (according to the WSJ article), with a max of $10,000 according to the website. The parents volunteer as well.
If you're interested in learning more, they are having two intro sessions on November 2 and December 1, 2011 at 6:30 at 301 14th Avenue (@Clement). You can learn more about their philosophy here.