They will retire or change careers to avoid the administrative workload, survey finds.
More than half of headteachers will leave the profession in the next four years, with many saying they have had enough of being bogged down by bureaucracy.
A survey of nearly 2,500 classroom teachers and school leaders found that 56 per cent of heads expected to retire in that time and 17 per cent intend to switch to a different career.
Now England's General Teaching Council (GTC) is calling for the Government to ease the burden on heads by cutting red tape.
The survey, commissioned by the GTC, indicates that more than 10,000 new heads will have to be found. It also revealed that few young teachers are willing to replace the departing heads. They blame the administrative workload.
Keith Bartley, GTC chief executive, said more needed to be done urgently to address headteacher recruitment. "Relieving the current administrative burden of the role will be a key part of this," he said.
John Peck, 59, who is retiring at Easter after 20 years as head of Peafield Lane Primary School in Mansfield, Nottinghamshire, said: "The league tables and high-stakes accountability really do get you down. I don't feel I could keep up this pace for much longer.
"So many of my colleagues are going at 55 now. Not many people stick it out to 60. I see too many of my colleagues going out through stress or forced out by the pressure."
The importance of school leadership has been increasingly recognised within schools, and in the Government's drive for school improvement and pupil progress.
The National College for School Leadership (NCSL) was established in 2000 to provide professional development for school leaders and to address the shortage of heads.
Chris Kirk, NCSL director of succession planning, said: "It is widely recognised that the 'baby boomer' generation of headteachers is approaching retirement age - and this means that identifying new school leaders is more important than ever."
Mick Brookes, general secretary of the National Association of Head Teachers, said: "People with a mortgage and a family aren't sure they want to put themselves in a position where their job is only as safe as the last set of results."
In the GTC survey, teachers rated the quality of school leadership as the most important factor in addressing underachievement.
Performance tables had the least impact in supporting achievement, with only 12 per cent of teachers saying they helped and most saying their impact was negative.
Mr Bartley said: "We need more valid forms of assessment that draw on teachers' expertise."
The NCSL has been at pains to point out that once teachers experience leadership roles they can find it enormously fulfilling.
Matthew Copping, 33, who is headteacher of Whitchurch CofE Junior School in Shropshire, said: "With every job there are stresses and strains, but the satisfaction of this job - in influencing the lives of children - is hard to beat.
"Young teachers need to think about the potential for them to make a difference to so many more children," he added.
Staff shortage fears, page 8
WE NEED A SUPERMAN, PUTTING OUT HIS HAND AND SAYING, 'STOP!' INSTEAD, WE HAVE COMMITTEES MEETING TO DECIDE THE COLOUR OF HIS COSTUME
- Peter Gordon, 57, head of Hazelwood Primary in north London, stepped down at Christmas after 13 years.
I stopped enjoying being a head. I was losing the ability to put things in perspective. Everyone has expectations because you're head. And nobody is looking after your interests. There's very little in the way of pastoral support and there's a lot of angst. Last time I took out life insurance, I had to pay an extra premium because I was a head. You're not a good risk.
I don't regret leaving one bit. It felt as if a 50-ton weight had been lifted from my head. But you don't realise it's there while you're doing the job. It's just part of your being.
In my last year, I just felt I didn't want to do it any more. I felt I was living in a world that was going mad. 'Stop the world, I want to get off!'
I've applied to become a witness intermediary. And I've enrolled on a comedy-writing course. I'm open to anything, really. In some respects, I feel the world is my oyster. I feel like I did when I first left college, many years ago. There's an enormous sense of anticipation.
I don't feel confident that the Government can do anything to stop people leaving. So many education ministers blitz through, introduce a whole load of reforms, then move on.
We need a Superman, putting out his hand and saying, 'Stop!' Instead, we have committees meeting to decide the colour of his costume.