If this is brought in, and it seems likely it will be, I've been thinking a lot about how it's going to shape things in future.
Personally I think it's outrageous to introduce it from day 1 and it should only be introduced immediately for new pupils who are not already in (or signed up to be in) the private system.
Parents should have at least 1 academic year of notice that VAT will be levied on their fees, as their child moves up through each stage of their education, between infants, juniors, year 7 or sixth form. Or in the case of public schools it would be moving from Prep to common entrance.
You should be exempt from paying VAT until your child reaches the end of whatever stage they are at, as it's a natural break with the opportunity to move into the state system with less trauma and disruption to the child. At least that way, you'd have fair warning and plenty of time to make alternative arrangements. People with kids in private junior school will be pushing really hard to get them through the 11+ and hopefully into a super-selective state grammar school, but plenty already do that anyway and only keep their children in private school from year 7 onwards if they are unsuccessful at 11+.
The disruption to children will be terrible if they get pulled out mid-key stage or halfway through the two year GCSE programme, or whatever. Getting a state school place anywhere within sensible distance of home, let alone a good state school place is going to be hugely problematic.
Obviously it goes without saying that very good or outstanding state schools will already be heavily oversubscribed. I can see private school parents pushing up property prices around outstanding state schools (or decent Community Schools where they are obliged to take you at any stage so long as you live in catchment) even more than they already are, or renting out their main home and moving into catchment of those decent state schools in order to secure a place.
Either way, there is no doubt it's going to be carnage.
I'm thinking that as Home Education or Home Schooling is already a burgeoning thing, lots will go that way. But most people who were previously in the position of being able to pay school fees probably don't fit the typical profile of most home educators. The private school parents are most likely people running their own businesses or earning high salaries in professional or corporate jobs that require their full attention, so they are probably not in a position to undertake the home schooling themselves.
I see these parents potentially banding together to create Home Ed co-operatives where they sign their children up to online learning schemes, then collectively employ freelance teachers as private tutors, rent workspaces and meeting rooms etc.
So their 'home schooled' children now learn with with maybe 10 or 20 other children, five days a week, dipping in and out of different sessions according to age and subject and which teachers are available that session, to oversee and supplement the online learning.
It wouldn't take that much to organise and it would be far cheaper than private school if enough families grouped together to fund it.