Accord, a campaign group which will be launched tomorrow, wants to persuade the Government to stop religious schools engaging in religious discrimination. It wants so-called faith schools to be open to all, with pupils, teachers and staff drawn impartially from all faiths and none. It also wants a common, inclusive religious education for all schools.

So far, so not-new, and characteristic of anything you might expect to hear from the National Union of Teachers or the National Secular Society. But the thing about Accord is that its ranks are swelled by religious individuals as well as professional agnostics such as Tessa Blackstone. The chairman is a progressive rabbi, Dr Jonathan Romain.

It is supported by the Christian think-tank, Ekklesia, whose co-director, Jonathan Bartley, said "often faith schools take pupils only from their own fath or even from their own denomination within a faith. For schools to advertise for someone of a particular faith that means that 90 per cent of the population will be ruled out straightaway."

Well, I have news for Mr Bartley. That's what makes a faith school a faith school. Actually, can we cut to the chase here? Most of them are actually church schools run by the Church of England and the Roman Catholic church – they're the ones that secular-minded parents are lying and cheating and going to church to get their children into.

But it's precisely the fact that they are discriminatory that makes them Catholic, or Anglican, or Jewish, or Muslim. A Catholic school in which the children are drawn impartially from all religious groups and none, in which the staff, from the head down, are no more likely to be Catholic than agnostic, is simply not going to be a Catholic school , period. It will simply be a school which happens to have a funny religious name and which has a distant historical connection with the Catholic church, by virtue of having been established by an order of nuns or whatever.

It will be impossible for such a school to have what is fashionably called a Christian ethos – because, believe it or not, such an ethos is not some sort of free-floating quality which happens to attach itself to a church school. It comes from the religion which is not just taught, but practised within it and which, if you take it on its own terms, is meant to help the children to flourish.

Of course a church school is discriminatory, in the way that any institution that has a particular distinguishing characteristic is discriminatory. A working men's club is discriminatory in the sense that it is not the Bullingdon Club. A Labour university society is discriminatory in that it is intended for people of a Labour persuasion rather than diehard Tories.

It may be argued that there are no laws to prevent Boris Johnson and David Cameron from joining a Labour club – but the advent of Conservatives into it would, I suggest, change its character quite markedly. The Women's Institute is remarkably inclusive – as long as you are a woman.

There is, of course, the usual argument that church schools engage in cream-skimming, or selecting pupils on the basis of their family background. Figures from the research group, the Centre for Economic Performance at the London School of Economics, suggest that on average in all English local education authorities, 17.3 per cent of pupils get free school meals; the average in Catholic schools is 12.5 per cent.

But as Sandra McNally of the Centre for Ecomonic Performance points out, the data do not prove that schools are socially selective. They might be. Or it might be that the people who apply to them are more likely to be middle class.

Church schools work. And given the patchy record of the state system, what we don't need to do is to tear the heart out of one group of schools within it that perform, in general, really well. Accord is simply a recipe for discord.