Looking for a new job can be a fraught experience. However, when starting in a new career such as teaching, it pays to know something about the background to the job market.

The labour market for teachers is big. There are more than 500,000 trained staff of working age. Well over 400,000 are working in schools; either part-time or full-time, and others are employed on temporary supply contracts. Finally, there is the PIT, or pool of inactive teachers, many of whom are working in other jobs within the education sector as administrators, policymakers, inspectors or academics.

Others are working in the media, publishing, social work or the law. For these people, a spell as a teacher has often been a useful start that has provided a breadth of understanding that they’d not have received if they had not worked in the classroom.

At present, the labour market is being tugged in two different directions by contradictory pressures. On the one hand, school rolls are falling. They peaked in the primary sector as long ago as 1999, but the downward trend was masked for some years by increased numbers in nursery and pre-school classes. However, if the demographers are correct, rolls in primary schools will fall by nearly half a million pupils over the next few years to reach a low point in 2011.

The decline in numbers probably started to affect the secondary sector this year, although some schools are still experiencing rising rolls. Overall, secondary rolls are expected to fall every year up to at least 2016, and possibly beyond. The size of the fall will be affected by any changes to the 14-19 curriculum or patterns of study such as a transfer of some students to the further education sector.

Not all schools are experiencing the same. The South-east and parts of London are areas where many new houses are being built. This benefits some schools as new families move in. By contrast, in other areas, estates that previously supported thriving primary schools are now almost child-free zones, and the local primary school is facing rapidly declining rolls. The effects of parental choice tend to exaggerate the trend in falling rolls as popular schools remain full and less favoured schools haemorrhage pupils at the end of every summer term.

There are reports from Wales that jobs in primary schools were scarce for newly qualified teachers last year, and there is no evidence to suggest it will be any better this year. However, in Scotland there are still job opportunities if the adverts carried by the English edition of The TES are anything to go by. Traditionally, teaching posts in Scotland have only appeared in the Scottish edition of the paper.

The effect of falling rolls by itself would lead to a reduced demand for teachers. Fortunately, the other trend in the education labour market is having the opposite effect. Increasing levels of retirement over the next few years will to some extent ameliorate the effects of falling rolls. The retiring baby boomers, many of whom joined the profession in the 1970s, will create some demand for new teachers. However, this demand will not be sufficient to prevent a reduction in numbers of teachers in training, unless there was a concerted effort on the part of government to reduce class sizes through additional funding.

One group who will benefit from the retirement boom are those who joined the profession within the past 10 years. Many of those retiring over the next few years hold middle and senior leadership posts. Most will need replacing, and promotion opportunities will abound, even in traditionally difficult areas such as primary schools and secondary school history departments. This term, we heard of one Group 3 primary school that received no applications when advertising for a new head, while another was rumoured to have received several hundred requests for details when it advertised a basic classroom teacher post.

The high level of retirements will only come to an end when the age at which teachers can draw their pension rises from 60 to 65. By then, the staffroom landscape will look very different. Schools will have more teachers under 30, and far fewer over 50 than at present. The loss of years of collective wisdom will be balanced by the enthusiasm of the new breed of teacher. However, policymakers will need to ensure that drop-out rates among teachers during their first five years of teaching are kept low or shortages may develop. A younger teaching force also means more teachers taking time off to start a family; and requests for maternity leave will undoubtedly rise from their present all-time low.

So, the next 10 years offer opportunities for teachers already established in the profession, but it may well be harder to get onto the first rung of the ladder, not only in the more sought-after areas but also in the inner-city schools that have found recruitment so challenging over the past decade. Of course, there may be a reaction to news that jobs for new entrants are difficult to find. The Government may discover that persuading graduates to enter teaching will remain a challenge. The reduction of 20 per cent in applications to primary PGCE courses in Wales this year could be a warning of worse to come for recruiters.

Almut Sprigade is an analyst with Education Data Surveys of Oxford