Long-serving, dedicated teachers whose classroom abilities have faded with age could be forced out of their jobs on competency proceedings if plans to scrap the compulsory retirement age go ahead, heads' leaders have warned.
Axing the "default" retirement age of 65 could mean otherwise successful careers ending on a "sour note" as heads will no longer be able to use age grounds to remove those who no longer measure up.
Brian Lightman, general secretary elect of the Association of School and College Leaders said: "The last thing we want is long-serving and faithful employees who are getting to a stage where they are tired ending up on capability proceedings.
"We need to be able to ensure that people who have served a long time leave with the right recognition, not on a sour note."
But he said this would only apply to a small minority of teachers, and very few would be likely to want to stay on past 65.
"Most finish before 65 because it is such a tiring job," he said.
And statistics suggest that, despite government plans to raise the state retirement age to 66, there will not be a surge in geriatric teachers in the coming years.
The latest official figures for 200809 show that only 2 per cent of teachers in maintained schools are over 60 and 10,700 teachers retired on age grounds that year.
The standard age for drawing the teachers' pension is 60, but teachers who entered the profession after 2007 will now have to wait until 65.
Only those who have come to teaching late in their working lives are likely to want to stay on when the retirement age is scrapped from next April, experts say.
Martin Freedman, head of pay and pensions at the Association of Teachers and Lecturers, said a few members expressed an interest in staying on past 65, but the majority approached the union to discuss early-retirement plans.
He said: "Mostly, it's people saying, `I've been working for 30 years, I have had enough'."
But he believes many older teachers feared the "cliff edge" of retirement.
"You have the situation where you are working on the Friday, it's your birthday on Saturday and you're out of a job on Monday," he said, stressing that many wanted advice on how to "wind down" their working lives, while drawing part of their pensions.
"There are many flexibilities already in place to do this," he said.
The news about plans to scrap the retirement age comes as former Labour Cabinet minister Lord Hutton prepares an independent review of public sector pensions.
Unions fear that the report's findings will result in raising employee contributions or even scrapping the much-loved "final salary" element of the scheme.
The NUT last week asked Lord Hutton to dispel the "myths and lies" about the cost of public sector pensions.
General secretary Christine Blower also expressed concerns that a recent move to base pension benefits on the consumer price index rather than the retail price index could cost a teacher on the average pension up to pound;30,000 over a 25-year retirement.
All of the main teaching unions have made it clear that the two-year pay freeze, combined with the end of generous public sector pensions, could tip them into industrial action in the coming months.
2% - Proportion of teachers in maintained schools aged over 60, according to most recent figures
`I don't know many other heads who have decided to stay on'
The TES columnist Mike Kent, aged 67, has been head of Comber Grove Primary School in Camberwell, south London, for the past 30 years.
He has been considering retiring since the age of 63, but somehow never manages it - he is just too attached to the school he has nurtured over decades.
He said: "I negotiate things year by year with my governors. I was definitely going last year, but now I'm definitely going next year.
"The school works so well. It's a nice school; there's lots of pressure for me to stay.
"Because the place works so well and over the years I've appointed people who share my philosophy, who I love to work with, we don't have too many problems - it's not overly stressful."
He said that working with younger children kept him feeling young. "They just bounce into school. I think it might be different in a secondary," he said.
"Whether you stay or not depends on the situation you are in at the time, whether you enjoy it.
"Education has been something I have enjoyed very much. I don't see it as work; it's a part of my life.
"I don't know many other heads who have decided to stay on - I think we are very few and far between."