http://en.wikipedia.org/wiki/Summerhill_School
Summerhill is noted for its philosophy that children learn best with freedom from coercion. All lessons are optional, and pupils are free to choose what to do with their time
In addition to taking control of their own time, pupils can participate in the self-governing community of the school. School meetings are held three times a week, where pupils and staff alike have an equal voice in the decisions that affect their day-to-day lives, discussing issues and creating or changing school laws. The rules agreed at these meetings are wide ranging - from agreeing on acceptable bed times to making nudity allowed around the pool and within the classroom
There is no concept of a "year" or "form" at Summerhill. Instead, children are placed according to their ability in a given subject. It is not uncommon for a single class to have pupils of widely varying ages
A documentary: https://www.youtube.com/watch?v=TxngqMavda0
site: http://www.summerhillschool.co.uk/