Will Labour actually gain some revenue for slapping VAT on school fees, or is it heading for fiscal embarrassment as so many private school pupils are decanted into the state sector that the taxpayer will suffer a net loss? The question has been batted around for months as everyone ponders a great unknowable: how many parents would throw in the towel when faced with a higher bill for educating Barnabus and Fenella, and send them to the local comp instead?

An early indication has been provided today by the Independent Schools Council (ISC), which claims that the number of pupils enrolled...