*But I don't see how an 'ordinary' person could possibly have the range of knowledge and skills, never mind equipment and resources, to cover all the subjects normally taught in secondary school.
And what about the clubs, societies, sports, music, drama, dance, field trips, overseas trips etc that school can provide, that would either be impossible or very, very expensive to provide in a domestic setting.*
Ferguson, the reality is that many, many home educated youngsters have in fact passed their IGCSEs, AS levels and A levels, despite their parents lacking specialist knowledge and skills, labs, etc. It can be, and is, done very successfully. I can't pretend to know the ins and outs of the more formal qualifications (as we're not quite there yet - my DC are younger) but it most certainly is done. These children go on to further education colleges and universities and successful careers. I've seen this with older home educated youngsters first hand in our community (which is not in the UK) but of course this is also true of the UK.
Second, regarding the clubs, societies, sports, etc: you need to understand that home educated children are usually part of a community and a very supportive one at that! My own home educated children belong to a wide range of clubs where they meet up with their home educated peers many times a week to do woodwork/design, ice skating, dancing, cricket, a wide range of other sports (football, rounders, volleyball, you name it), choir and crafts. We have a regular nature club, bookclubs and loads of outings organised through our local facebook page and informally in our own closer networks. Then there are the birthday parties, sleepovers and ad hoc playdates - it is busy, stimulating and very sociable!
People who are outside the home ed community really do seem to believe our home educated DC are isolated when nothing could be further from the truth.