When the Reverend Tim Hastie-Smith meets his colleagues at next week's gathering of independent school "premier league" heads, he can expect to be a talking point. The chairman of the Headmasters' and Headmistresses' Conference (HMC) has just announced his departure from fee-charging Dean Close in Cheltenham to move to Kettering Academy, one of the Government's favoured state schools.
"I want to get outside my comfort zone," says Mr Hastie-Smith. "It is a school surrounded by its clientele and there is real opportunity to serve a community. It is a wonderful challenge, particularly if the academies programme offers as much independence of leadership and management as it appears to."
He doubts whether the six-figure salaries on offer are the main reason why independent heads move to academies. Academies may be able to match salaries but not benefits. He will lose the house and benefits that go with his present job.
Four academies have so far signed up independent school heads. So, is a new chapter opening in the heads' transfer market? Can the head of highly selective Winchester College, for example, run an inner-city comprehensive? And vice versa?
A report that analyses HMC schools, to be published at next week's conference, underlines the differences between the roles. Professor Alan Smithers, its author and director of the centre for education and employment research at Buckingham University, says: "Independent school heads are able to do what they feel is right for their pupils. State school heads have to comply with a number of requirements that are imposed centrally. The former feel they are professionals, the latter technician managers. State schools are finding it hard to recruit heads, but there is a lot of competition to run independent schools."
The attraction of academies, says Professor Smithers, is that they are the Blair government's "attempt to reproduce independent schools in diluted form". Bernard Trafford, head of the independent Royal Grammar School in Newcastle upon Tyne, agrees that freedom is the key.
"The Government says academies are free, but they are not as free as we are," he says. "Maintained heads now manage their own budgets, but I can't get my head round the number of funding streams that go into state schools. Another huge difference is that we don't have to deal with the same level of alienation. I don't know that I could handle dealing with large numbers of dysfunctional families."
But he believes some independent school heads could succeed in comprehensives, and vice versa.
"School leadership is school leadership," he says. "Heads have transferable skills. Sometimes governing bodies are not as open-minded as they should be. There's no special skill involved in dealing with parents just because they are in 4 x 4s."
The lure of freedom brings a steady flow of state heads into independent schools, mainly grammars. This year, four out of 24 new HMC heads have come from state schools. But headships of big HMC schools are usually the preserve of the independent sector. Governing bodies tend to be cautious. Martin Stephen, high master of St Paul's School in west London, says there are good reasons for that.
"In my experience, the best heads in the maintained sector are equal or superior to independent school heads," he says. "But we patronise each other to say that we can just swap roles. We are fooling ourselves if we pretend that they are not very different. I would not recommend running St Paul's or Manchester Grammar to someone who did not have experience of the sector."
The differences, he says, include the "truly alarming amount of reporting in the state sector" and the time his state school colleagues have to spend on governing body politics. Links with parents are also different if they are paying customers.
Heads are more likely to move between the sectors if they work in girls' schools. Jill Berry, head of Dame Alice Harpur School in Bedford, who becomes president of the Girls' Schools Association in January, has worked in four state and two independent schools. She says heads from the two sectors can swap roles. There are differences, of course - for example, the time she spends on recruitment and marketing. "It's like being a salesman for a product I believe in," she says.
As one head told Professor Smithers in a report last year: "The forces I need to respect most are market forces - what the parents are saying about us at their dinner parties."
Could a comprehensive head run Eton? Ms Berry believes so. "It would be a huge learning curve, but every new job is a huge learning curve because every school is different," she says. "Much of it is about dealing with staff and dealing with children. It is about emotional intelligence, communication skills, common sense, listening."
Ms Berry thinks both sectors would benefit if more teachers worked in both.
How would more cross-fertilisation help? Martin Stephen says the maintained sector could learn about providing a fast-track for the most able, and the independent sector about behaviour. Geoff Lucas, HMC's secretary, says the Government should fund partnership schemes for state and independent heads to shadow each other.
But Ms Berry believes it will take time to break down barriers. "There is huge prejudice on both sides," she says. "If I had not moved into the independent sector, I would have all kinds of assumptions. I might believe that independent education should be abolished."
The move from independent to state school is much harder than the reverse because of state regulation, says Mr Lucas. "Independent heads have the ability to hire and fire, to take decisions about their intake, freedom over the curriculum and speed of decision-making," he says.
Above all, Professor Smithers says, "state school heads are vulnerable to the capriciousness of government".
CAREER PATHWAYS THAT CROSS THE SECTORS
Martin Stephen, high master of St Paul's School in London. Educated at Uppingham School in Rutland
1971: English teacher at Uppingham School
1972: Housemaster and English teacher at Haileybury in Hertfordshire
1983: Second master at Sedbergh School in Yorkshire
1987: Headmaster at Perse School in Cambridge
1994: High master of Manchester Grammar School
2004: High master of St Paul's School in London
Jill Berry, head of Dame Alice Harpur School in Bedford. Educated at Wath- upon-Dearne Grammar School in Yorkshire, which became Wath Comprehensive while she was there
1980: English teacher at Range High School in Formby
1986: Second in English at Wirral Grammar School for Boys
1989: Head of English at Altrincham Grammar School
1993: Head of sixth form at Queen Elizabeth's High in Gainsborough
1995: Deputy head at Nottingham Girls' High School
2000: Headteacher of Dame Alice Harpur School in Bedford.