Yuk - selfish, stupid, dogmatic people setting up huge problems for their poor offspring in the future.
I didn't see these children doing anything that most well-supported children don't do with their families. It was very telling when SD asked the mum what she thought the eldest child was learning when playing in the woods (to justify their very alternative attitude to education, I mean). she was only able to say 'Well, he's learning about himself'. OK.
I was a Forest School leader and I've brought my children up to experience nature as fully as possible. I was also a school teacher and agree that conventional schooling is far from ideal - especially since the National Curriculum and SATS! So I understand that some people feel it can be deadening for children's spirits.
But children need to be educated if they're going to live in 21st century Britain. And they need friends and common experiences (ie school!) to help them connect with their peers. Whatever the reservations about schools, I think it's misguided to deny this almost universal experience to your children. Good grief - you can add as much value as you like out-of-school in terms of experiences in nature, or encounters with culture - art, music, literature, dance etc etc.
I really felt for those trapped children. I couldn't help thinking the whole set up was more to do with their parents' needs than theirs. I've encountered parents before who preferred to keep their children away from school because THEY wanted them around.