Robin Barrow examined research into teaching techniques and concluded that “what has and is being done by way of empirical research is inadequate to tell us anything secure and important about how teachers ought to proceed in the classroom.” The major shortcomings, “its conceptual inadequacy and the inappropriateness of systematic observation techniques to the subtleties of human interaction”, would apply to any research into class size. Decisions are therefore going to have to be made on the basis of common sense.

The first common-sense point to be made is that the size for a group depends on the activity in which the group is engaged. If the activity is watching a film, then a school of 2,000 could do this together. In fact, larger numbers heighten the effect of watching a film or a football match. However, to play a football match the games teachers will not want more than 22 active participants. Other activities can be even more demanding. When I teach the piano I have to take one pupil at a time.

An English lesson is made up of a variety of activities that do not all require the same size of group. I can give a spelling test to 60 pupils without difficulty. I can read a story to 60 pupils, and there is a good chance that they will get as much out of it as if I were reading to 10. I can supervise them to read it for themselves. But suppose I want to class-read a Shakespeare play? There is a limited number of characters in each scene, and while those who have a part are likely to be fully engaged, those who don’t may get bored.

When it comes to creative writing, the teacher should be able to give help and advice to individuals as and when they need it, and therefore for this activity the smaller the group the better. English also encompasses speaking skills and the ability to lead a group and to work in a group (a requirement of the national curriculum). This activity puts a limit on class size.

All this assumes that the class is behaving itself and that those in it are motivated, an assumption that cannot be made in a majority of classes in a majority of schools. Where trouble-makers are present they can make more mischief in a class of 40 than in one of 20. At the heart of the teaching-learning process is the relationship between the teacher and the learner. Where there is a poor relationship, then the quality of learning is also likely to be poor.

Real learning comes through teacher and pupils struggling together with a body of material. This is a co-operative activity. The smaller the numbers the more effective it is likely to be. This does not mean that very good teachers cannot achieve good results with a large number of students. Perhaps they can. But we have to optimise the effectiveness of ordinary teachers, not super-pedagogues.

We may not be able to give hard figures for class size but we can be pretty certain that for activities other than watching films and videos, taking dictation and tests, or listening to the teacher rabbiting on, a group of eight is more likely to lead to better learning and understanding than a group of 30, assuming that the teacher takes advantage of the possibilities that working with smaller numbers allows.

All these things are well-known to teachers and pupils. In the absence of reliable research we will have to turn to them. They are the only people who have first-hand experience of the issue. And if we cannot trust the common sense of teachers, how do we justify entrusting them with the futures of our children?

Teachers are reluctant to strike because they do not want to alienate parents. But a short-term disruption of classes is surely preferable to a long-term endurance of large classes? The argument, as everyone knows, is not really about class size but about money. If a piece of research were to be published tomorrow showing that small classes were better than big, would the Government be thrusting money at schools and telling them to employ more teachers? Of course not. They would be commissioning another piece of research to contradict the first one.

Colin Hodgetts is consultant at Human Scale Education