I see the private school parents and desperately trying some mental gymnastics to try to criticise this policy.
I'll say it again
Fewer than the IFS predicted will leave, demand for private education is highly price inelastic.
No, private schools won't stop doing bursaries or free lets to the community. Bursaries and scholarships are basically a business transaction anyway, those kids get great results and enhance the reputation and image of the school which encourages parents like you to send their kids there. For most private schools, bursaries are not paid from fees but from endowments. They'll need to keep doing all these things to retain charitable status.
No, there won't be a massive amount of pressure on the best schools in the most desirable areas, there will be so few children leaving.
No, there won't be house price increases in these catchments either, the people who send their kids to private schools already live in the nicest areas in town. No one who can pay on average 90k over 6 years for one child's education is making a financial decision to live in an area that is less than optimal for sell on prices.
No, it won't impact nursery, university, after school, extra curricular or holiday clubs.
Your mental gymnastics is very funny to watch, but it really is the most meaningless of rubbish.