For the past year I have worked as a supply teacher while studying for a masters degree at the Institute of Education in London. Apart from regular days in a couple of schools where I teach maths - that’s my subject - I often get work by ringing an agency at 8am each day. It can be quite rewarding to arrive somewhere new at 8.50am and within minutes be giving a lesson to a bewildered class you’ve never met. It can even be fun.

But it isn’t always so - sometimes because of my inadequacies as a teacher but more often because of a school’s low expectations of me and of the pupils.

Before my studies I taught for five years near King’s Cross so I’m used to the city and to classroom routine. Even when you’re only in a school for a day you can get a sense of its ethos. Some, which I’ll call “learning” schools, exist to give the children an education. Others do not - and this is borne out by the children’s behaviour, the attitudes of the staff and the expectations of me when I arrive. The prime concern here is control: control of pupils and obedience to the most inane rules. Subservience to teachers is seen as far more important than the encouragement of learning.

When a class teacher is away, a form of revenge is meted out on his or her replacement. In “learning” schools this may come down to three or four cheeky individuals, a bit of paper-throwing or too much noise. But for most pupils the desire to get on with their work takes over.

In the “control” schools, it can take 15 minutes before the class even begins to take notice of my (by then) shouting as if the release from their normal regime is too much for them. Almost every request from the supply teacher is resisted or ignored. You don’t know the school and so they’re going to behave badly. Why? Because they can and you probably won’t be back tomorrow.

Why don’t I follow it up with the teachers in the school? Because they expect you to have trouble and the most you’ll get is a sigh of resignation. The assumption is that you are there to exercise crowd control. The work set is derisory, to you and the pupils. It is often a pile of worksheets; one for each lesson every time the teacher is absent, irrespective of whether the content is relevant.

In “learning” schools, the work is relevant and challenging for the pupils - and for me to teach. Often it is the work the pupils would have done with their ordinary teacher. If there is a disruptive pupil, the staff provide constructive support; discussion with the pupil about the effect on his or her work and the damage to other pupils’ progress. In a “control” school the child gets a sermon, often as much about school uniform or the breaking of some other irrelevant rule as with the original disruption.

A major difference between these two schools is the way staff relate to me. In some schools I have gone all day without meeting the head of department. In others, he or she has gone through the day’s work with me, checked with me during breaks, and advised me about any difficulties.

My experiences are not unusual there are a lot of us about. My concern is the wasted opportunity through not making full use of cover teachers’ skills which makes children think rules exist for their own sake and which doesn’t put learning first.

Alan Sharland lives in north London