I'd be very interested to know how many children people know of who are definitely leaving their private school for a state school - not people with plans to do so in future years, solely those definitely going now / in 2025.
For myself - large Scottish all years school, I only have knowledge of my early primary kids's classes - no-one leaving so far (but I'm guessing early primary may be less affected as Labour have been signalling this policy for a while so you wouldn't start if you couldn't afford VAT).