It now seems likely that Tony Blair will go into that election promising rapid expansion of academies.

Though many supporters of comprehensives will be alarmed at the prospect of private school involvement, this policy should not be dismissed out of hand. Any genuine attempt to involve the independent sector in raising achievement of our poorest children deserves support. Some independents have a fine record of offering scholarships to disadvantaged children and may well see academies as a way of extending that mission.

Even so, it is easy to be cynical. The Government is looking for an eye-catching re-election policy that will attract aspirational parents, traditional “swing” voters who would be impressed by a shiny new “Eton Academy” down the road. Meanwhile, the independent sector’s charitable status, which provides valuable tax breaks, is under government threat and it is keen to earn brownie points. The mutual interest is obvious.

A bigger objection is that academies, especially those linked to highly-selective independent schools, will add a new top tier to the state system. A new academy costs around pound;30 million, twice as much as a “bog standard” comprehensive. But this may be a price worth paying in communities where other schools have failed.

In the end it is a matter of trust. But Charles Clarke will struggle to convince critics that Downing Street shares the vision he set out last year, of a system in which all secondaries can be specialist and “where excellence is a spur to equality, not its enemy”.

Academies may, or may not, provide the spur needed to put under-privileged pupils on an equal footing with the children of merchant bankers, but one very practical question remains: what exactly are the skills that a public school can bring to a struggling inner-city comprehensive? Answers on a postcard, please.