According to the High School of Glasgow (private) website:
Broadly speaking, the average cost for private day schools is £4,980 per term, or £14,940 per school year.
(20% VAT on top of that would amount to just under £3k.)
That doesn't include boarding. I am definitely all in favour of imposing VAT on private schools. VAT is meant to be a tax on luxury items and it would indeed be a luxury in the eyes of many working class - and even middle-class - families to be able to afford to educate one's children privately, and if they can afford £15k per year they can almost certainly afford another £3k.
A lot of the typical private-school users are very like the family of some of my friends at uni. They were lovely guys and very down to earth but their families' businesses meant their accountants could work the books in such a way that everyone in the family was privately educated yet they still managed to get a grant to attend uni.
And, of course, there's more to the education than the teaching, learning, facilities, etc. It also buys certain privileges via 'the old school tie' connections.
The guys I knew at uni were more than aware of this. When we were applying for teacher training we had to go through a 40-minute rigorous interview. The head of the panel was a senior member of staff at the private school these guys attended. We were coming out of these interviews pretty shell-shocked. These guys were telling us their interview consisted of a handshake (not a masonic one, just an 'old friend' one) and a "How's it going? You're in, by the way." That is a verbatim repetition of what one of them said to us.
Education has changed, though, beyond recognition. I went to a Senior Secondary (a Catholic one for the best qualified boys in the Catholic primaries in the entire county). It was harsh, disciplined - not that we didn't get up to stuff - and very focused but I was doing stuff in first year that I ended up trying to teach to senior pupils at comprehensive schools without much success.
I put that down to Primary Education of the era. I was doing long division in P3 or P4 and was parsing sentences in P5. (For the uninitiated, imagine the scene from The Shawshank Redemption when Andy is trying to teach the young gallus inmate how to break down a sentence. Expressions like "subordinate clause of reason" were no strangers to us.
I was doing subjunctive verbs in my second year of Spanish. By the time I was finishing teaching I wasn't having to teach them at Higher level in a language in which they are in common usage.
But these are all symptoms of a society that is in freefall.
All the great civilizations bring about their own downfall. Modern Western society is heading the same way.
Rant only just started but I'll restrain myself...