The Sudbury Valley School has been in operation for more than 30 years now, and several other schools around and outside our country (the United States) see our school's success and are modeling their schools on ours.
The school accepts students from ages four and up, and awards a high school diploma. It is a private school, which relies upon tuition and does not engage in fundraising. Studies of our alumni show them to be "successful" by any criteria; most have gone on to their first choice career or college, most have a comfortable income, and (the best definition of success, in my mind) most are happy people.
The physical plant is a beautiful Victorian mansion on a ten-acre campus. It is furnished like a home, with couches, easy chairs, books everywhere (rather than hidden in a library), etc. The grounds are excellent for sport and games, and the school has several facilities; music rooms, an art room, a high speed Internet connection, a darkroom, a piano, a stereo, a pond great for fishing, several computers, etc.
Students (from age four on up) are free to do as they wish during the day, as long as they follow the school rules (more on school rules later). The campus is "open" and most students come and go as they please, without having to check with an office or other such nonsense. No one is required to attend classes and, indeed, classes are rare and bear little resemblance to the usual notion of a "class." There are no tests or grades of any kind. Students and staff (teachers) are equal in every regard. The students and staff refer to each other by first name, and the relationships between students and staff can't easily be distinguished from the relations between students.