Government ministers reject this concern, claiming that there is no research evidence to show that a change in class size affects pupil learning. They cling to this dearth of evidence, because to reduce the average size of primary classes from the 1993 national average of 27 to say 24 would require about 26,000 more teachers at an annual cost of Pounds 400-Pounds 600 million.

Many of us believe, of course, that this is just the kind of serious investment that is needed to improve young children’s preparations for tomorrow’s world. Since the total national cost of primary education in 1991-2 was Pounds 7.6 billion such an increase seems possible.

To support this level of increased expenditure, good research evidence would be helpful, to say the least. It is not surprising that to date there is little home-produced empirical evidence about the effect of class size on pupil progress, because there have been no widely used and effective measures of pupil progress.

There are, however, strong theoretical arguments which school governors must be made familiar with if the tide of increasing class sizes is to be stemmed. Here are six ways in which a primary class teacher’s work changes when one or more child joins the class.

* For every lesson involving individual work one or more set of materials has to be prepared.

* Every time written work or an exercise is set, there is one more piece of work to read, mark, think about, and discuss with the child.

* In national curriculum assessments there is one more child to assess and one more report to write to parents and discuss with them.

* There is one more child involved in the regular routine of classroom activities such as notices-to-parents-and-returns-to-collect, lost property to find, misdemeanours to sort out, children’s’ quarrels to resolve, first aid to administer, questions to answer.

* There is one more child to share in that small amount of time which can be spent by the teacher on focusing on the needs of the individual children and there is the ever-present chance that this extra one will be one of those who makes disproportionate demands on the teacher’s attention.

* There is one more space filled in the classroom which may reduce the flexibility for organising teaching in different ways, and extra furniture in a typically cramped classroom reduces the space for everybody.

What are the consequences of this for the class teacher? Patience is stretched, end-of-the-day tiredness is increased, creative energy sapped, and time for planning reduced. This can mean that extra-curricular activities (after-school chess club, book club, drama, netball, football) are reduced. Also resistance to illness may be reduced.

What are the consequences of these effects on the class teacher for the education of the children? There is a greater chance of children wasting time and becoming frustrated because the teacher is busy elsewhere. There is an inevitable reduction in opportunities for learning through the teacher’s delivery of the curriculum being more fraught than with a smaller class. If extra-curricular activities are reduced, this is a loss for the children. If the teacher is sick there is a loss of continuity in the curriculum.

The above arguments demonstrate that larger classes reduce the opportunities for children to learn from their teacher. The question is, by how much?

This is where empirical research is needed. This summer, for the first time, widespread information can become available. In 1991, 500,000 seven-year-olds in England and Wales were assessed in English, mathematics and science at the end of key stage 1. This summer, the same children, now four years older, will be assessed at the end of key stage 2 in the same subjects. The question can be asked, how do the children taught in larger classes compare with those taught in smaller classes?

This will be a minefield for researchers. Questions about the validity of the assessments, the sizes of the steps between the levels, and the different classroom and social contexts will bedevil the researchers, but the raw data could be easily collected from schools.

Take one example of the kind of inquiry that might be mounted. In mathematics in 1991, 65 per cent of the key stage 1 children were assessed at level 2. By 1995, a few may still be at level 2, but most will have progressed to higher levels. As the steps between the levels are not regular it will be best simply to divide these 325,000 children into two groups, those who progressed from level 2 to level 3 or less, and those who went from level 2 to level 4 or higher. These two groups can then be analysed first into socio-economic divisions (which are known to affect classroom achievement) and secondly according to the average size of class the children have been in over the past four years.

Similar analyses can be done for those who were at level 1 and at level 3 in 1991, and likewise for English and science. From these sets of results the vexed question of how significant class size really is may get some reasonable answers. More local and detailed studies might link these findings to different teaching methods used by the schools.

Research like this could give a crude indication of what it might cost (in terms of change in class size) to raise by say 10 per cent the proportion of children moving from level 2 mathematics to level 4 or above in different socio-economic situations. Or it might show that class size is not as important as teachers, parents and governors think.

Dare the Government fund such research and publish the results?

Michael Bassey is an emeritus professor of education of the Nottingham Trent University, general secretary of the British Educational Research Association, and a governor of Lowe’s Wong junior school, Southwell, Notts, which this year and last has had to reduce staff and increase its class sizes.