I wrote my letter of resignation in January. I hadn’t won the lottery, got a fantastic promotion or decided to travel the world. I didn’t have a job to go to or any firm career plans; I just knew I had to leave. Some people think I’m mad. And why shouldn’t they? In just three years I’ve become a curriculum leader and assistant head of year. I have a flourishing career in a good profession. And though I hesitate to say this, because teachers aren’t accustomed to selling themselves, I think I’m good at what I do. I also like what I do.

I am proud of the profession and my colleagues. It is an exciting time; educational standards are rising and teachers’ efforts are beginning to be recognised and rewarded. My own school has just received an award for exceeding its targets and has rewarded staff with a cash bonus.

The establishment of beacon schools is another encouraging move towards improving standards and performance. And the huge expansion in communications, particularly in new media, has provided increasing opportunities for teachers nationwide to share good practice. So why leave?

It has little to do with money - financial incentives for graduates are only a short-term solution to the current recruitment crisis. It is crucial that the Government instead recognises the issue of long-term retention - and realises that money alone will not keep young teachers in the profession. The Department for Education and Skills estimates that 48 per cent of teachers are due to retire in the next 10 years, while figures from the General Teaching Council show that two out of five teachers quit within five years.

No one goes into teaching for the money. New recruits may be swayed by financial incentives, but the staff they need to retain are those - like me - who entered teaching without any financial incentives. Most of us were motivated by altruism, not money. That’s why we’re in the classroom and not in the City.

Ask any young teacher what they need more of and they’ll say time: planning time, marking time and thinking time. I am an English specialist, but I’ve also had to become a specialist in media studies. I consider myself to have two areas of professional expertise, but my status is unrecognised and rapidly declining.

No academic or professional specialist would be left to stagnate the way teachers are. University lecturers take paid sabbaticals, conduct research, write papers. Doctors do the same. Barristers are paid extortionate hourly rates for “thinking time”. Teachers are expected to muddle along somehow, without being able to read and research their subject.

To improve the learning of others you need to be learning yourself, and this is where time becomes your enemy. If you are career-minded and take on additional departmental or pastoral responsibilities as I have, the teaching - the job you are there to do - becomes secondary. Lessons become mere “interruptions” to the perpetual preparation, assessment and bureaucracy. Somehow, the idea that teaching must be an all-encompassing vocation has seeped into our collective consciousness, but teaching should be a job, not a vocation.

Lawyers are highly respected, but we don’t usually talk of them having a “vocation”. So are architects, accountants and dentists. They have a career, but they do a “job” which has boundaries. Teaching doesn’t have boundaries. In the current climate, teaching seems to mean adopting a way of life akin to a religion. Effective teaching requires 100 per cent devotion and commitment, and if that means working 80 hours per week, then so be it.

And so you have the irony of the media studies teacher who rarely watches TV or finds time to read a newspaper, or the head of English who can’t find time to read a book. It’s all encompassing and non-negotiable. You can’t put the work away, you can’t “finish it”, and that leads to a cycle of guilt that clouds your free time. You forget how to be a person.

Our European counterparts seem to understand that teaching can be performed effectively as a “job”. In France, for example, contact time with students has a ceiling of 18 hours a week leaving ample time for research, planning and marking. Teachers are not required to be on-site unless they are teaching. All this contributes to their profile and status; the profession is highly regarded and over-subscribed. Estelle Morris take note.

I very much want to be a teacher and there are many things I love about teaching. But I also want a life. I’m essentially altruistic, not egoistic, but I want a “job”, not a “vocation”. I feel like a rat deserting a sinking ship, but I can’t let guilt be the reason for staying in a profession that has left me exhausted and disheartened. Teaching desperately needs passionate and motivated individuals. It also needs to recoup its professional status by once again making its teachers respected experts in their field. Until the issue of time is addressed, the recruitment and retention crisis will continue.

Janet Murray taught at the Bennet Memorial Diocesan school in Tunbridge Wells, Kent. In October she starts a periodical journalism course at the London College of Printing