Induction threat to profession
All new teachers have to complete an induction year before they can become fully qualified. But short-term supply work does not count towards induction, and teachers can only do four terms on supply without being inducted.
That means finding a supply contract of one term or more - which agencies say heads are reluctant to offer - obtaining a permanent job, or quitting teaching.
Despite The TES's record jobs' section this week, teachers in some parts of the country are unable to secure a long-term position.
Agencies report that heads are put off by the costs of inducting staff who will not be with them for long. Many are already dealing with the cost of the long-term sickness which has forced them to hire supply teachers in the first place.
One agency - Select Education - said only 40 of its 1,350 new teachers had started induction - yet 850 of them were working in schools the week before Easter. Managing director, Bob Wicks, said: "If nothing is done soon, the profession stands to lose at least 2,000 teachers."
The situation for NQTs still to start induction is likely to get worse as some 25,000 teacher-tranees look for jobs as they near the end of their courses.
Ministers are already concerned at the profession's drop-out rate. Up to 30 per cent of those who have completed teacher-training never set foot in a classroom.
Recruitment expert Professor John Howson said the system could ill afford to lose so many. "What is the Government going to do with these people if at the end of their four terms they haven't started induction? Are they just going to write them off?"
Supply is a growing field: figures show 16,600 "qualified occasionals" were working in January, compared to 14,100 in 1999.
The Teacher Training Agency said the probation year was intended to reduce dropping out by giving teachers a firm foundation. "A programme of support and monitoring needs continuity and, by definition, this is not available on a series of short-term placements," said a spokeswoman.
But Margaret Stewart, 23, who has worked in 25 schools in the Newcastle area since gaining her primary PGCE last summer, believes there are benefits: "I've got a lot of experience that I don't think I would have gained in just one school," she said.
"But it's worrying. I would be very disappointed and angry if I couldn't teach any more."
First Appointments pages 2, 3