Oh right, so now that you've reached a dead end on the bullshit about the state subsidising private schools - when it's actually the other way round - you've moved onto the next dogwhistle. Charitable status.
You know that VAT exemption has nothing to do with charitable status, right? It's education which is exempt from VAT. Same in pretty much every country throughout the world (those countries that don't exempt education from VAT subsidise private education to make up for it. And I don't mean your made-up kind of subsidise. Those other countries actually give the private schools money).
As for 'charitable purposes', schools charitable status is similar to religions. The diocese of Southwark, for example, is considered a charity even though I can't see much giving from them apart from preaching their religion. Which is arguably less useful than educating the next generation.
I'd actually be OK with those schools which are charities changing to some other structure, if there was a sensible way to do it. They don't get anything significant from being charities. There isn't a sensible way to do it, though. Like fuck does the government get to appropriate assets which were donated by someone hundreds of years ago for a specific purpose, and have been built up by parents and donors since. That would be blatant theft.
Also, I think our society would be less culturally rich if we created an artificial barrier on what is and isn't a charity. There are quite a lot of random little charities which do things like restore windmills. Not particularly 'important' in the grand scheme of things. But it's a part of British culture I like.