I'm looking for the same thing, I also live in LA, the Valley to be more specific. My sister, who is 12, has been going to Oakwood since Kindergarten. It's a pretty good school, but I'm not that impressed. It's pretty elitist. I'm not sure if you are wealthy or not, but everyone who does to that school has lots of money. I wouldn't feel comfortable with my daughter going to a school with people from only one socio-economic class. They are also big on homework, since about 3rd grade she has had homework that takes a few hours for her to complete every night. One thing I like about the school is that in 7th grade she is learning about revolutionaries and revolutions, the Chinese Revolution, the Cuban Revolution, Indian Revolution. I want to read most of the books that are required from this year. But over all, that aren't much different from any other school, I wouldn't consider them very progressive.
Pacifica Charter School in Culver City sounds really awesome, here is a link: http://pacificaschool.org/
I've heard good things about Children's Community School in Van Nuys.
There's also Play Mountain Place which again, I've heard good things about it. Here is a link: http://www.playmountain.org/
It's based partly on the Summerhill school.
This is probably the school that my daughter will go to next Sept. unless some outrageous charter school opens up near my house. It's a montessori school, Kinderhaus Montessori. Here's a link: http://montessoripasadena.com/
There is also a charter waldorf school on the westside that I heard about. I forget the name, but I can look it up if you are interested.