This might work with older kids who have been to regular school and therefore have experienced some form of structure and discipline, but I feel like this would be terrible for kids going from k-12. Overworking kids and teens can be bad for the mental state and make them feel less motivated, but I think this can be too. Kids need freedom, but they also need more structure. There just needs to be a balance. From what I've seen, Scandinavian schools seem to be the best example, though I wouldn't know for sure because I don't know anyone who grew up for the majority of their lives in any of those countries.
Awesome, there should be more of them. Free schools make kids active and not passive, they learn how to trust themselves, their feelings and opinions and be truly independent.