Supply teachers fear they are becoming an endangered species as the school funding crisis bites and heads start to turn to cheaper cover.
Agencies are confirming a significant downturn in the market and The TES website has been flooded with messages from anxious staff worried about where their next posting will come from.
The news follows last month's announcement that TimePlan - one of the biggest agencies - was making 9 per cent of its administrative staff redundant with tight school budgets cited as a reason.
The past few weeks have confirmed the decline. The beginning of the academic year is traditionally a quiet period for supply work, but both teachers and agencies say bookings are down compared with this time last year.
School funding problems appear to be the main factor. But the workload agreement, allowing schools to use cheaper assistants as "cover supervisors", has also come into force this term leaving supply teachers fearing for their long-term future.
One disgruntled teacher wrote: "It's obvious that supply teaching as an earner of regular income is on the way out."
Another said: "If this situation continues we will be unable to sit at home waiting for the phone to ring.
"We will be forced into some poorly-paid job just to make ends meet. So when schools do need the services of a proper, qualified teacher there will not be one available."
Pauline Chambers, managing director of Teacher Workline, a medium-sized supply agency covering London and Birmingham, said: "The market has obviously dropped. In terms of everyday business we are very quiet. There just aren't as many vacancies about."
Long-term placements, less affected by seasonal trends, were also down - by 25 per cent compared with summer term, she said. David Rose, a spokesman for Select, one of the country's biggest supply agencies, said demand had dropped since last year particularly in primary schools.
"There is definitely an issue with budget cuts and heads are finding other ways around the situation," he said.
"A lot of in-service training has been cancelled and we are finding that many primary heads and deputies are taking classes themselves.
"The number of instructors and teaching assistants is also increasing and there is some evidence of them having whole-class responsibility. I see that as a trend that will continue."
He said there was no discernible geographic pattern to the fall in the market. Like the funding crisis it was hitting schools all over the country.
Geoff Brown, director of education at Dream, another national agency, began to notice a drop in demand at Easter.
He was also concerned that while schools had previously gone for the most suitable supply teacher whatever the cost, some were now being forced to take on "inexperienced and inappropriate" staff.
But both Dream and Select are continuing to organise overseas recruitment trips. "There is always a demand for quality, experienced teachers somewhere," said Mr Brown.
The prospect of a pan-London supply teaching service was discussed at a seminar this week. Participants were told that the scheme would probably ultimately involve the appointment of several supply agencies as preferred suppliers.
The agency, which organised the meeting, is a partnership between 15 local education authorities and Go Temping, a private company that provides the necessary technology.
Drying of Supply, Jobs 1