The issue of incompetent teachers is as old as the profession but was ignited 15 years ago when the then chief inspector of schools claimed there were 15,000 of them.
Chris Woodhead's estimate has been repeated many times since, but The TES can for the first time reveal how many teachers are being dealt with in official competency proceedings across the country.
More than 3,200 teachers in England have been through the process over the past five years, according to figures collated from freedom of information requests to all local authorities. Poorly performing school staff received in excess of #163;2.3 million in pay-offs and severance packages during the same period, the data reveals.
The total of 3,253 teachers is far higher than the number of teachers referred to the General Teaching Council for England (GTC) for being substandard. Just 14 teachers have been struck off for incompetence since 2001.
Huge regional variations are also revealed, with hundreds of teachers in some areas being subjected to competency proceedings compared to just a handful in other parts of the country.
West Sussex launched the highest number of cases, with 385 over the past five years while Oldham recorded 211. But in Somerset, Rotherham, Middlesbrough, Telford and Hampshire, just one teacher went through official proceedings.
Similarly, 38 local authorities made severance payments, while others have a policy of not paying out to those accused of incompetence.
The biggest spender was Darlington, at #163;196,400. Six other councils - Warrington, Suffolk, Cumbria, Cornwall, Manchester and Worcestershire - each paid out more than #163;100,000.
Reasons given to The TES for invoking competency procedures include lack of pupil progress, unsatisfactory Ofsted inspections (applying to headteachers), poor relationships with children, conduct at meetings, and teachers being unwilling to "move with the times".
The new figures account for responses from 123 of England's 152 local authorities. They show that 273 teachers were fired or signed compromise agreements in the past five years, while around 550 resigned from their posts. The figures also show that 357 teachers showed improvement following competency proceedings, which begin when less formal attempts to improve performance fail.
Unions have attacked the system as an "excuse for bullying". They have said pressure on heads to achieve top exam results is leading them to use competency proceedings as a "blunt instrument" for getting rid of teachers - often unfairly.
Amanda Brown, head of employment at the NUT, said the regional differences reflect the "management culture" in individual local authorities. "It's obviously not a fact that teachers in some areas are more incompetent than others," she says.
"We've seen some robust and aggressive forms of management in schools when it comes to competency proceedings, and this shows they are managing the process very differently. We now have a culture of transformative headship, as encouraged by the Government, and this has resulted in this kind of management style. It makes people feel under pressure."
The current guidelines for competency proceedings were drawn up a decade ago, with the aim of getting rid of regional variations. A number of heads have demanded it be updated as it can still be difficult to manage, including a call from heads' union the NAHT for the process to be limited to a maximum of eight weeks (see box). The Association of School and College Leaders also wants the process to be "streamlined".
One head from Leeds - who did not want to be named - who has been involved in two competency proceedings, says: "It involved a huge amount of time from me as headteacher and from one of my assistant headteachers. It also alienated some other staff.
"It is a strange human reaction: people want something done about their under-performing or lazy colleagues. However, when the managers start taking action, there is a groundswell of support for the "victim" of the management's "bullying".
"It is the one key area of school improvement that remains very, very difficult. My view, and I believe it's shared by many other heads, is I would love to see the process simplified and reduce the power of the unions. Employees need protecting, but not at the expense of children getting an excellent education."
A head from Surrey, who also did not want to be named, says: "The dilemma for schools is that the Ofsted expectation is that all teachers should be good or better, whilst capability cannot be used if the teacher meets satisfactory standards."
It is a long-held concern that poor teachers are "recycled" around the system, moving to different places rather than being dealt with in their existing schools.
It is not known whether the vast majority of the estimated 820 teachers who were dismissed, signed compromise agreements or resigned remained in the profession and, if so, where they ended up working.
All teachers who are fired or resign while going through competency proceedings should be reported to the GTC by their local authorities.
However, that system appears to be failing, as the most recent figures from the GTC show that between June 2001 and September 2010, a total of just 201 teachers have been referred for alleged incompetency: 173 from local authorities and 28 from schools. Following investigations by the GTC, only 81 cases have so far been deemed serious enough to warrant a hearing.
Some heads have taken personal action in an attempt to stop incompetent teachers taking up posts in other schools. One contacted by The TES agreed an #163;8,000 severance payment after informal competency proceedings, on the condition that a reference would not be provided.
"Without this latter agreement to effectively prevent him from getting another teaching job I would have pursued competency procedures," the head says.
"Although it was more costly, it was preferable that he resigned rather than returning to teach and going through competency procedures. In this way the children were not negatively impacted by the process."
Some teachers subjected to competency proceedings went on to teach in the private sector. One school business manager from Herefordshire, who had to deal with four members of staff going through the process, says: "Three of these obtained jobs at private independent schools - which would be better suited to their teaching methods, and one at a FE college. I am confident that all four have been more successful in these new environments."
Heads who are not up to scratch go through the same process. One 57-year-old in Gloucestershire had the process instigated by the chair of governors after an unsatisfactory Ofsted report. It went on for six months before it was decided the head did in fact meet the criteria for the job.
One Hertfordshire head, who asked to remain anonymous, said that because it is a high-performing local authority, teachers find the idea of competency less "daunting". "Teachers who go through it either re-engage or move on," he says. "If you are not teaching efficiently, then it's one of the most depressing jobs in the world."
West Sussex County Council said the reason for the high levels of competency proceedings in the area was to "maintain high standards".
The NASUWT claims the use of competency procedures is often triggered for the wrong reasons. "We are getting more and more complaints, and we are concerned they are not being used appropriately," says general secretary Chris Keates.
"Heads are using it as a blunt instrument for inappropriate reasons. We get many reports that it's just an excuse for bullying. Teachers who find themselves going through competency proceedings might just be inappropriately deployed. It's important to remember that under-performing doesn't mean incompetent."
According to Dylan Wiliam, emeritus professor of educational assessment at London University's Institute of Education, all teachers should be asked if they want to improve and anyone who answers "no" should be fired. "Teachers who do not believe that they can improve are much more dangerous than incompetent teachers, because to protect their self-esteem, they end up blaming the students," he said (see commentary).
The Government has pledged to limit entry to teaching to those with at least a 2:2 degree, believing that better qualified teachers will have more success in the classroom. Whether that will have a long-term impact on those struggling with basic performance remains to be seen.