There are more teachers in England than ever - and they are getting younger and younger.
New statistics show the changing face of the profession, which is now more youthful, but still overwhelmingly female.
The figures, released by the General Teaching Council for England (GTC), are collected from all those working in 19,739 schools in England, and from those who have recently qualified as a teacher.
Figures for 2011 show a fall in the number of older teachers and a continuing trend of school staff becoming younger. It is the final year the GTC will publish a detailed breakdown of the teaching profession before it is axed next March.
The proportion of those in the profession aged 50-59 has dropped by 8 percentage points in the past five years. The number of teachers aged 39 and under has increased by 7 percentage points during the same period, with more than a third now under the age of 35.
The ageing of the profession has been a considerable concern for a number of years, with experts warning of a demographic "timebomb" that would see large numbers of retirements.
But according to Professor John Howson, a teacher supply expert and director of Data for Education, the shift to a younger workforce will also be the cause of difficulties for headteachers.
"Retirement is no longer the big worry, but the fact that around half of women in both primary and secondary schools are between 21 and 39 creates a planning dilemma in respect of calculating numbers expected to take maternity leave each year," he said.
Professor Howson worries that an increase in the use of temporary teachers could create problems for schools.
"We've now effectively reached a stage where half the profession is of child-bearing age," he said. "This, combined with the rights to longer maternity leave, will lead to schools having to employ temporary staff to replace them.
"It could be very challenging to recruit these people in some areas of the country."
But Brian Lightman, general secretary of the Association of School and College Leaders, says a younger workforce is "not a negative thing".
"It gives schools opportunities to bring in very high-quality graduates," he said. "The cost of employing people close to retirement is also higher."
Chris Keates, general secretary of the NASUWT, said a more youthful workforce was leading to many older teachers feeling unfairly treated.
The TES has previously reported that experienced teachers - who attract higher salaries - have been targeted by some schools looking to cut costs as their budgets come under pressure.
"Many older teachers, particularly those with younger headteachers, believe they are excessively monitored and are made to feel that they have nothing to contribute," Ms Keates said.
"But younger teachers themselves can also be victims. A higher proportion are on temporary contracts, while headteachers keep their options open. This isn't good for them, and it's not good for stability of the school."
EMPLOYMENT: Jobs stalemate
It is "concerning" that a significant number of new teachers are still not securing permanent jobs, according to GTC chief executive Alan Meyrick.
Almost 13 per cent of NQTs are working in supply, down just 1 per cent from 2010. A total of 9.3 per cent of all those in the profession are supply teachers.
"We hear from many new teachers who have difficulty securing permanent employment and struggle to successfully complete the required induction period," Mr Meyrick said.
Brian Lightman, general secretary of the Association of School and College Leaders, said heads were finding it difficult to employ the same number of people due to the economic situation.
"This is particularly the case in some non-English Baccalaureate subject areas," he said. "People have trained in good faith and they are finding it difficult to get jobs."
GENDER: Men missing from primary schools
One in four primary schools still has no registered male teachers, and there are six secondaries with all female staff, the GTC figures reveal.
A total of 4,569 schools have no male employees, the census shows, down from 4,700 in the previous year. There are only 48 men employed in state- run nurseries, and only three are under the age of 25.
The teaching profession as a whole remains "predominantly female", with women accounting for 75 per cent of those in service, although there are more male newly qualified teachers - up 2.4 per cent since 2008.
GTC chief executive Alan Meyrick said there had been little change in the "long-term imbalance" between the numbers of men and women.
"Women are still under-represented in senior management roles within schools," he added. "We need to attract teachers and promote tomorrow's leaders from the widest possible pool, regardless of gender, so that children can benefit from the greatest talent and experience."
Original headline: No country for old men: teaching stays female but gets even younger