Although I’d always enjoyed my job, I had no intention of doing any more teaching. I looked forward to a complete career change. I wanted to live in a rural idyll and write. And so I did, until the local secondary school asked me to help.

An English teacher was taking four months’ leave and the school had no specialist to fill in. I happily agreed, thinking it would give me an introduction to a new educational scene and supply me with some very welcome money. What I didn’t realise was how harrowing the experience would be.

In the first few days I was helplessly inadequate, exactly the type of teacher of whom previously I’d been contemptuous. The ineffectual supply teacher who nags and shouts at classes had always had my censure. I’m not talking about difficult classes here, but pleasant, motivated students who suddenly turned into kids from hell. I always blamed the supply teacher.

Many didn’t come back and I never wondered why.

Well, I know now. I walked into my first classes with the confidence of the innocent and immediately hit the wall of, “Great, a supply teacher!” As the days went on, I began to recognise the glee in the eyes of the pupils when they saw a stranger at the front of the room. One boy, seeing I was not his regular teacher, made a beeline for a cupboard and, to the delight of his classmates, swept all the folders in it on to the floor.

Other problems involved changing names and seats and claiming to have already done the work set - all familiar to any teacher who has ever covered for another. The difference with the supply teacher is that she has no reputation. She desperately needs the support of the disciplinary structure of the school.

It took me weeks to attain quiet, hardworking classes, and that was in no small way due to the help of a very supportive department that believed me when I told them I could teach; that, in fact, I was once quite good at it.

I dragged myself into school every day, sometimes having had little or no sleep, and gradually things began to improve. In the course of all this, I learned a great deal and came in contact with many supply teachers who will never go into schools again.

This is a desperate waste of talented professionals who would rather drive taxis than enter a classroom again. Imagine a situation in which we could not staff our local GP’s surgery because locums were regarded as less qualified by staff and patients alike. The idea is ludicrous.

If we don’t want the supply system to disintegrate completely, we must first of all change attitudes. When, after many weeks, I reached the stage of actually having conversations with my classes, one of the most frequently asked questions was how I was going to manage not having a job when the permanent teacher came back. I explained carefully that I had come in to help out - not to make a career of teaching in their school.

Students must be made aware of this - that the supply teacher is a valuable commodity which schools cannot do without, not some burnt-out case desperate for the money.

This message must be conveyed to all staff. Any misbehaviour of students who have a supply teacher must carry instant sanctions. Sanctions must be well publicised and the reasons highlighted to students, staff and parents.

In other words, the supply teacher must be regarded as a visiting expert and treated as such. The school discipline policy should incorporate specifically the special position of the supply teacher.

It is true that some supply teachers I have seen have taken the easy and lazy option of “babysitting” rather than teaching. Schools can, however, deal with them easily by not inviting them back - a luxury they don’t have with permanent teachers.

I have gone back this term. I have made new friends and enjoyed learning new systems after so long in one school. However, I do not intend offering my services to any other school - at least until attitudes towards supply teachers have changed.

leadership 28 Jennifer Baker was head of faculty in a Lancashire comprehensive and now lives on an island in the Inner Hebrides