It is by stealth that things change in England. Nobody ever voted for a privatised dentistry service. No party, so far as I can recall, even proposed one. Yet over large areas of the country, a wholly private service is effectively what we have: when a new NHS dentist opened in Scarborough in February, 300 people queued for hours to register. They did so in the knowledge that an NHS dentist will do for pound;19 a filling that would cost pound;90 in the private sector. Four out of 10 dentists now refuse to take new NHS patients.

NHS dentists, like GPs, have always been self-employed. Unlike GPs, who received a fixed amount for each patient, they were paid piece-rates: their income depended on the number and type of treatments they carried out. (In both cases, the payment systems have been slightly modified.) Tthe NHS rates are now so low that dentists are forced to go private to earn a decent living. This is at best a half-truth (after expenses, they get around pound;50,000 a year). True, John Major’s government gave the first impetus towards privatisation in 1992 by cutting the money dentists received from the NHS. But the real story is that over the past few years hundreds of practices have been taken over by private, profit-making chains, such as Oasis Healthcare. These chains have an obvious reason to get as many patients as possible paying privately. They have been so successful that most dentists’ income now comes from private practice, against only 5 per cent as recently as 1990. Could something similar happen in schools? Look at the ambitions of Global Education Management Systems (Gems). It has 20 schools in the Middle East and now plans a chain of private schools in the UK, charging fees well below those found in the established independent sector.

The company has also, as The TES recently reported, approached the Department for Education about running profit-making state schools.

Ministers firmly ruled out the possibility. So far, so good. But Gems is likely to sponsor two of the Government’s city academies. Though it says that its interest is philanthropic, the company’s schools director has admitted that running academies will help to establish the company’s brand.

The problem for new entrants to the independent schools market has always been to overcome parental distrust of the untried and unknown. Association with a government programme would establish the company’s credentials.

There is another possibility. Suppose the company’s city academies are heavily over-subscribed. Might the company not be tempted to steer disappointed parents towards its private schools? And might a future Tory government not be tempted to ask why, for two very similar, Gems-branded products, one set of parents should pay at least pound;5,000 a year and another set nothing at all? And might it then propose to allow vouchers (which the Tories say they will introduce) to be used in both types of school?

I do not say that any of this will happen or even that it is likely to. But I think new Labour should draw a lesson from what happened to NHS dentistry. Give a private, profit-making company just a foothold in a state sector service, and it will do everything possible to ease that service into private fee-charging. It is in the nature of the beast. Schooling is an enormous potential market which, even outside the state-controlled sector, remains almost entirely closed to profit-makers. Private capital would love to get its hands on it. Watch very closely lest it steal our schools as it stole our dentists.

Peter Wilby is editor of the New Statesman