After battling against the teacher recruitment crisis in the South-east, David Eyre, a headteacher in Berkshire feels he can at last pause for breath. A year ago he was struggling to find teachers as staff turnover at the Desborough School in Maidenhead, hit 20 per cent. “Gate fever gripped my staff,” he says. “Once it got beyond the point of one or two people moving for perfectly understandable reasons, it suddenly became almost like a panic, people thinking everybody’s going.”

Now the school is nearly fully staffed with only one supply teacher in a total teaching staff of 63. But the 11-18 boys’ comprehensive has to live with the legacy of its recruitment blitz. The school’s budget will go into deficit this year and the influx of new teachers has put more pressure on the school’s experienced and senior staff.

There are nine newly qualified teachers and two on the graduate teacher programme, as well as six from overseas who are working towards qualified teacher status. “There are very few we have taken on who are tailor-made, ready to do the job and with the benefit of several years experience,” says Mr Eyre. “They need mentors and they need support from senior staff, so there’s that hidden cost. There’s the time that I’m not spending, and my senior staff are not spending, on other issues in the school. It’s huge amounts of extra work.”

One in three teachers expects to quit the profession within five years, the General Teaching Council for England has warned. More than half of those surveyed in a Mori poll said their morale was lower than when they joined the profession.

Carol Adams, chief executive of the GTC, said the challenge was to keep teachers in the profession and called on the Government to develop a coherent retention strategy to match its recruitment strategy.

The Government prefers to see the glass two thirds full rather than a third empty. “Recruitment to teacher training is at record highs,” David Miliband, the school standards minister, told the North of England Conference (in January).

“Of course retention strategies are important but nearly seven in 10 stay for at least 10 years. Let’s not fall into the old trap of always talking ourselves down.”

But a growing concern for some heads is the hidden costs and knock-on effects of the recruitment and retention crisis - its effects on school budgets and particularly the pressure it puts on experienced staff. The Wavell School in Farnborough, Hampshire, made headlines 18 months ago when it spent more than pound;23,000 advertising teacher vacancies for the autumn term.

The head, Spokey Wheeler, a member of the Secondary Heads’ Association national council, says the crisis has not gone away. So far this year five adverts for a head of RE have yielded only one expression of interest and no interviews. It has also placed the school in an inflationary pay spiral. In his bid to recruit a deputy in design technology, Wheeler says he is under pressure to pay the same as he does some of his existing heads of department. “We need to recruit and to do that we need to pay over the odds. But what we’re doing is simply taking part in an inflationary spiral. And in doing that, what is the impact on the staff already in the school?

“Four years ago my head of special needs was on scale two. Today the same post is a four. And I could look at a significant number of other posts where we have up-rated the allowances for the departments.” The Wavell school has four trainees on the graduate teacher programme - part of a policy to “grow their own” good quality teachers. “If they’re in a deemed shortage subject, then we will get funding from the DfES to pay the salary of those individuals,” says Mr Wheeler.

“What it doesn’t pay for are the costs of my teaching coach and the amount of time that’s undertaken. And 14 of my middle managers will be voluntarily giving up time to mentor those individuals over and above what the programme says.”

Redbridge in north-east London says some of its schools are caught in a vicious circle. Because they are short of experienced teachers and don’t have enough mentors, they are unable to support initial teacher training. This puts the training burden on other schools which do have experienced staff. One of the borough’s secondary school has 14 newly qualified teachers.

“It does add to burdens,” said Kelvin Wilson, recruitment strategy manager for Redbridge. “I have seen the situation where schools run increasingly on the experienced staff they have. When that pool starts to get smaller and smaller then it pressures everybody through the system.”

This extra pressure could be the last thing senior staff need. The most vulnerable group in the profession - those most likely to leave - are those who have qualified but are in their first years in the classroom.

The next group identified by the GTC survey as at risk of low morale are the over 45s. And those experienced teachers who have constituted the backbone of the profession are also the ones who have missed out on the recruitment incentives. At the same time, they are the ones bearing the brunt of the hidden costs of recruitment.

The issue was highlighted by Phil Willis MP, Liberal Democrat shadow secretary for education, in a speech to last week’s North of England education conference in Warrington.

He said the exodus from teaching of those with between six and ten years experience threatens to turn today’s crisis into a catastrophe. “It was always said if you survived the first five years you were a teacher for life - not any longer,” he said.

“These are the school leaders of tomorrow and they are leaving. Not surprising when they have missed out on training salaries, secondments, advantages of shortened pay spine, yet subjected to a level of intimidation and abuse that in any other walk of life would not be tolerated.”