Because then they can be nationalised - a solution which, I have long believed, is the best way of ending Britain's unique educational apartheid. After Northern Rock, nationalisation is back in fashion and, for the schools, it suddenly looks like a practical proposition.
Until recently, most people thought that if schools didn't like the requirements for charitable status, they could simply opt out, lose the financial benefits, and either raise fees or increase class sizes.
Not so. The land and buildings, it is presumed, were intended for charitable purposes. They are in trust. They cannot be used for the convenience of what would become a private business. "The law does not allow a school to walk away from being a charity and take assets with it," explained Dame Suzi Leather, chair of the Charity Commission. "We can take those charitable assets and redistribute them."
I accept nationalisation may not be exactly what she has in mind. But I hope the commission would ensure the assets were used mainly for children within the state system. They could be sixth-form colleges, or schools for children in boarding need, or centres where every child in a local authority area could spend a week. Or perhaps they could be sold off or let and the proceeds used for education maintenance allowances or university bursaries. The precise use is irrelevant, as long as it potentially advances the education of the mass of children, not a moneyed minority, and is therefore genuinely charitable.
An advantage of the nationalisation solution is that it breaches nobody's human rights. Parents would still be free to pay for private education. They would have to find it in more modest and probably more modern institutions, not in richly endowed foundations that were set up for quite different purposes. Britain would then be free of the leading public schools and what makes them so damaging: their associations with social class and inherited privilege, their old-boy networks, their (in some cases) geographical isolation, the exclusive culture imbibed through their boarding houses, and the brand image that leads everyone to assume their superiority.
Ideally, all children would attend schools with peers of differing abilities from socially mixed backgrounds. Research suggests that would improve performance across the board. But we shall not easily achieve it in the near future. In the meantime, we should rid ourselves of those few dozen schools that hog a disproportionate share of university places (Eton has taken nearly 400 at Oxbridge in the past five years), elite jobs and, when Conservatives are in power, cabinet positions.
Some will object that the schools would reconstitute themselves and set up again, perhaps abroad. If they did so, which I doubt, it would be on a diminished scale, since the capital, and particularly the land, required to replicate them would be beyond the means of all but a handful of billionaires. Eton could re-open in Manchester, Munich or Marseilles but, without the playing fields, it wouldn't be Eton.
Yes, I know it's a dream. The schools will not commit hara-kiri and the Charity Commission won't dare go ahead with expropriating them.
But it's 20 years since I last thought it worth writing about the nationalisation option. At least we can dream again.
Peter Wilby is former editor of the 'New Statesman' and 'The Independent on Sunday'.