We just interviewed at the Sudbury Valley School in Framingham, MA--the original Sudbury. Our 4 yo will attend this spring for one week as a guest student, and the decision will then be made as to whether that's the school for him.
They had an industrial kitchen,. an art room with a pottery wheel, loads of libraries, a music barn, a garden, and little flocks of barefooted kids (in Oct!) running around. 8 year olds playing 4-square with teenagers. We're really hoping that it lives up to the reputation, and we'll see how it goes in April.
The 4yos can attend the weekly meeting, and they have full voting power. They also have the right to send a complaint to the Judicial Committee if wronged by another student, and to have that complaint fairly heard and acted upon. They're also expected to follow any decisions handed down by the committee if they act inappropriately toward another student as well. What I saw, mostly, were older kids respecting the little ones or just ignoring them and letting them run around like little fairies!
I also think it's an extension of our life. We're debating home schooling but if we do send him to Sudbury we'll enrich him at home, through teaching him our interests (chess, cooking, computers, reading, writing) and nurturing his interests.