"a just about good enough school is usually preferable to even the best home education."
Skegness, I hope you appreciate how very, very lucky you are to have this view.
You have clearly had a very positive experience of education so far, and I truly hope this continues for you.
However, for some children and their families this is absolutely not the case. My son (who has been HEd now since Oct 08) was neglected and abused throughout his entire school career till I finally pulled him at the start of Y5. He had a dx of ASD from age 7 (and by God, did we have to fight to get that) which nobody within the LEA would accept or support. Even when the head at his first school described him as 'the most violent child with AS I've ever known' she still didn't see the need to give him help. I could tell you horrific tales of his experiences and I'm not alone.
I appreciate that without knowledge of the way HE works, and without the negative experiences of school education that have prompted parents to deregister their children for HE, you are unlikely to grasp the advantages of it as an education choice. In many cases, as ours, it's the ONLY choice where the state refuses to accept a child's SENs and won't provide for them. But please do not assume that any school education is better than HE. My son was on a fast track to a life of prison for his violence and nobody in the statutory system was prepared to lift a finger to help him. Since being HE his life has been transformed. His academic ability is flourishing, he's producing work of a standard I couldn't have dreamt, his social life is excellent because he can now cope with after-hours activities that he couldn't handle in the past because he was so freaked out after a day of abuse in school. He is becoming more independent because he is encouraged to think for himself instead of toeing the line in the chicken factory. He has friends for the first time in his life and he has a future.
While I agree that there are some 'odd' families who choose to HE for their own reasons and don't prepare their children for adulthood, bear in mind that we're not all like that. Every family who home educates is different so please don't make assumptions and apply misconceptions and stereotypes to us. And avoid assuming that all parents who send their children to school are encouraging and supportive and that they'll all turn out ready for the adult world.