It's received wisdom in teaching that if you want to get on, you have to move. Onwards and upwards. But too many moves and there are questions about your stickability. Too few, on the other hand, and you look like a stick in the mud.
So how long should you stay in a job? "Historically, it always used to be two years in a teaching job: one year to get to know the job and a year to consolidate. Then it was OK to move on," says Sherridan Hughes, a former maths and PE teacher who is now an occupational psychologist and careers consultant.
"If you move more often, there is always going to be the question of why?" says Sherridan, who works for Career Analysts. "You have to have a positive reason for wanting a move."
Legally, you are only required to give two months' notice to your current school. Resignations have to be made before three cut-off points in the year: October 31, February 28 and May 31.
In theory, if you really dislike a job, you could be in and out of a school in a term. But you run the risk of seriously prejudicing your career. In some cases, a quick departure may mean your letter of application goes straight in the bin.
Chris Healy, headteacher of Balcarras School in Cheltenham, says: "If someone is applying for a post here and has been at their current school for less than two years, I wouldn't even look at their application."
"I would be sceptical about someone who has gone to one school to be promoted, and is then looking to be promoted within a couple of years of being on staff there. I would say that is acting in their own self-interest rather than the interest of pupils they are working with."
His is a successful school and so Chris can afford to be choosy. By the same token, however, his staff are equally marketable, so anyone he invites to join his 90-strong staff is asked to commit to four years' teaching at Balcarras.
Staffing continuity is the key to any school's success, says Chris, who has been the head of the 1,300-pupil comprehensive for 12 years.
"I'm not looking for itchy feet. I'm not looking for the career builder. I'm not attracted to the careerist. I like people who enjoy the job they're doing," he says.
"If somebody applying has done six years at their current school and is promoted during that time, I would feel that was more impressive than if they had been in two schools and promoted in one of them."
But there is a growing body of teachers who, if they are ambitious, can't afford to hang around if they want to get on.
Latest statistics show that a third of secondary school teachers entering the profession are now over the age of 30. At the same time, three out of four assistant heads are under the age of 40.
If you factor in three years as a head of department, that doesn't leave many years to rise through the ranks and try out different posts at different schools.
Professor John Howson, director of Education Data Surveys, believes there is nothing wrong with teachers who join the profession in their thirties moving quickly - but once they are in a senior position, they should stay for at least three years.
"You have to demonstrate a degree of stickability somewhere," says Professor Howson, who answers questions from teachers on The TES online Careers Clinic (www.tes.co.ukcareer). "Someone will be looking for evidence that you've not walked away from the mess you made at your last school. They want evidence that you can see something through."
But, of course, people don't just move for their career. With an increasing number of households dependent on two teacher incomes, if one gets a promotion in another area forcing a move, then the other has to move too. And this doesn't always fit in with the two to three-year time frame.
Phil Revell, chief executive of the National Governors Association, says: "A teacher may want to move because they see a particularly good opportunity. They might be moving to be closer to their family - or to be further away."
Phil, who moved schools after two years as a then probationer to spend 19 years at a school in Shropshire, says this is particularly true of young teachers.
"A lot of young people will look for their first job reasonably close to where they may have done their training. And they will be at that stage of their lives when they will be making decisions about where to live and where to establish their careers and family and personal commitments. To penalise someone for this is ridiculous. You should look at the strength of their CV, the strength of experience they bring to the role.
"Your vision of what teaching can be will be limited by staying in one school. This also allows you to make your mistakes and leave them behind."
But sometimes teachers confuse improving their prospects with the need to move to another school. Just moving within the school you're in to a new position of responsibility can be enough.
"The Government has encouraged people to think that moving on is the way to get on and the way to succeed, but it's bad advice," says Chris Healy. "I prefer people to build careers by achieving things in schools they are working in."
Adrienne Niblett has done just that. She joined Balcarras five years ago as a newly qualified teacher - and stayed. "When I became a teacher, it was thought that you should be looking to move on from your first job after three to four years," says the 27-year-old. "I want to move up the ladder and progress, but above all, I want to be a good teacher. If you move too quickly, you're not able to fully establish yourself.
"I have been lucky to stay here because of opportunities that have come up."
In London, it's a different issue again. Kirsten Taylor became deputy head of The Green School, a voluntary-aided girls' school in Isleworth, when she was 34.
"A lot of the reason why I became a deputy quite young was because I'd always said: 'I'll do that' to any opportunity that came up." Kirsten joined the 800-pupil school in Hounslow, south-west London, as head of year in 1999, at the age of 28, having been a head of year at her previous school for three years. She became an assistant headteacher in 2002.
She was advised to stay in her first teaching job for at least three years. But today, she says, the climate is different - particularly in London, where people are taking on more responsible roles at a younger age.
"The pros of staying put are that you really can get to know the school, learn your craft and become the teacher you're going to be. That's what makes a school a success. The cons of staying too long - in the careerist climate - are that some people will say you have become too cosy, especially if you are in a nice school."
Kirsten says that heads and deputies are looking for people who have taken on extra responsibilities, both curricular and pastoral, at their current school - even if they have not been paid to do them.
If a teacher has moved around a lot, Kirsten says that would not stop the school interviewing them and giving them a chance to explain their moves.
But what about when you have made it to headteacher? Phil Revell believes there's a serious danger when a head regards their role as a job for life. "From a governor's point of view, if your headteacher has been in post for seven or eight years, it's like a good marriage - you have to re-energise it. Otherwise you end up like Guy and Madonna and fall apart."
But when you move is an individual choice. "For every person who moves too soon, certainly in the primary sector, there are other ones who don't move enough," says Professor Howson, who has written Taking Control of Your Teaching Career (RoutledgeTES).
"The bottom line is that the only person interested in your career is you. If you want a structured occupation you should go into the civil service. What teaching does is give you the ability to pick and choose which jobs you go for, and map your own career. If you miss a particular boat, it's not the only one in the harbour."
But just don't be too hasty about jumping ship too soon.
HOW TO TALK UP FREQUENT MOVES
Sherridan Hughes of Career Analysts advises:
DON'T run down your current school or employer - or past ones.
DON'T say: "It's a rough school, that's why I wanted to leave."
DON'T give the impression that you are running away from something.
DO say that you want additional responsibility.
DO be positive.
DO emphasise an aspect of your job you have very much enjoyed - and that is why you want this move, because it will increase the challenge in your career.