Yet the Government and civil servants in the Department for Education say they are wrong. Gillian Shephard, the Secretary of State for Education, told the Commons last month there was no research evidence from this country to show that big classes mean lower standards.
Some of Mrs Shephard's Conservative predecessors took a different view. Rab Butler's 1944 Education Act imposed a limit on class size of 40 in primary schools and 30 in secondary and its accompanying regulations said these should be lowered when circumstances allowed. The legal limit was revoked in 1959.
During the Eighties, declining pupil numbers ensured that class sizes in England and Wales fell but for the past five years those in primary schools have been rising steadily. More than a million primary children are in classes of over 30 and more than 11,000 in classes of more than 40.
Only Turkey and Ireland in Western developed countries have higher pupil/teacher ratios in primary schools. Our secondary classes are just above average size.
Moreover, a survey of 11 of our economic competitors, conducted by the Research and Information on State Education Trust and published earlier this month, shows that all but Australia have tried to address the question of class size.
Denmark, Finland, France, Germany, Greece and Norway have some legislation on maximum class size. For primary schools, the maximum ranges from around 25 to 30. Scotland has a normal class limit of 33 imposed through the teachers' pay and conditions agreement. Sweden has just abandoned its national limit so that class size can be decided locally. In the Netherlands and Portugal there are rules about the classroom space allocated to each child.
So are other countries right to worry about class size? Peter Mortimore, director of London's Institute of Education, says: "There is proof that class size makes a difference for the youngest children. The jury is still out on whether the same is true in secondary schools."
In a paper in the latest issue of the Oxford Review of Education, Professor Mortimore and Dr Peter Blatchford use American research to show the importance of small classes in the early years. In a study of 7,000 pupils in 79 schools in Tennessee researchers followed pupils from the ages of five to eight in small classes (13-17), regular classes (22-25) and regular classes with a full-time helper and teacher. Pupils in the smaller classes outperformed those in the other two in reading and maths. Those in the first year of compulsory schooling (six-year-olds) benefited most.
The findings contrast with large-scale studies in Britain over the last 30 years which have tended to show that pupils in larger classes did slightly better than those in smaller ones.
However, there could be other explanations. Popular schools in middle- class areas tend to be full while children in struggling inner-city schools may be in smaller classes. Many schools put slower pupils in small classes and better teachers tend to be given the bigger ones. Professor Mortimore's paper argues that the American research, which makes allowance for these factors by allocating pupils and teachers randomly to classes, is the most reliable we have. Even so, it proves only that the youngest children do better in small classes. Evidence about older pupils is less conclusive.
Reducing class size is expensive - around pounds 1m to reduce each class by one child, according to one chief education officer. Some research suggests that money would be better spent in other ways - on one-to-one tutoring, for instance.
We also need to be aware that smaller classes are not a panacea. As the Mortimore paper says: "One worry might be that reduced class sizes could maketeachers lives easier without necessarily improving the quality of teaching of the curriculum."
Research has to be done in England to discover whether the Tennessee findings apply in this country and to examine the effect of small classes on secondary pupils. Professor Mortimore has asked the Department for Education to fund such research but, so far, it has said no. The reason given is that of expense.
As the past ten days have proved, class size is so important to normally docile parents and governors that they are prepared to break the law. Could it be that ministers are refusing to fund research because they are afraid it will give the wrong answers?
THE VIEW FROM THE CLASSROOM
The five- and six-year-olds at Springfield Lower School in Kempston, a suburb of Bedford, are taught in two classes of 27 with another 12 pupils taught in a corridor outside the classroom, to keep down class sizes.
At the end of this year, a cut in the school budget will mean it will have to lose two teachers on temporary contracts because it can no longer afford to pay them, so next September the first years will be in classes of 36 and 37.
Springfield Lower knows all about the effects of large class sizes. Its current year three group, the seven- and eight-year-olds, are in classes of 36 and 37.
Annette Fisher, Springfield's head, says: "The parents have been wonderful about it. They are very supportive, but they are very angry that the school finds itself in this situation. There is a feeling of helplessness."
Springfield is a popular school in a mixed surburban area south of Bedford. It has 377 pupils on roll compared with a technical floor capacity for 360 children. Between 28 and 29 per cent of the children have English as a second language, mostly children from families of Punjabi origin.
At the end of this year, the school will lose 92 children and admit 72 - which will take the numbers down to the size the school is built to cope with but will mean a pounds 33,000 loss to the school budget. Hence the loss of the two teachers.
This is before losses it will sustain as a result of the Government's refusal to provide money to pay the teachers' pay award or to increase education spending in line with inflation.
"Teachers know their job is to teach whatever comes in front of them, but large classes are very frustrating," says Mrs Fisher. "There are only so many minutes that the day can be divided into, only so much time for dialogue with individual children. Then there are the children who dominate, who can take away minutes from the ones who don't.
"If you want quality, you need resources. In a large class, the children don't get the amount of time with the teacher that they should get. Class size does matter, particularly in those early stages of education.
"At the other end of education, in secondary and higher, classes are smaller. Yet if large gaps are built into the foundations because of large class sizes at the beginning, those small classes higher up won't matter. The foundations for future success are not there."
WHAT THE GOVERNMENT SAYS
I do not believe there is any proven connection between class size and the quality of education.
Eric Forth, Education minister, to the Commons, 1994
There is no research existing in this country which shows marginal increases in class sizes harm standards.
Gillian Shephard, Education Secretary, 1995
A relatively minor issue.
Kenneth Clarke, Education Secretary, 1992
Tim Eggar, Schools minister, when asked if he would take action on class size, 1991
WHAT THE RESEARCH SAYS
Reducing class size to the point where student achievement would be likely to benefit is prohibitively expensive.
Professor John Tomlinson, Warwick University, 1990
Large reductions in school class size promise learning benefits of a magnitude commonly believed not within the power of education to achieve.
Gene Glass and May Lee Smith, Far West Laboratory for Educational Research, USA, 1982
The outcomes of this research effort (into the connection between class size and educational attainments) have been conflicting, inconclusive and disappointingly meagre.
Dr Clare Burstall, director of the National Foundation for Educational Research, 1992
Drastic class-size reductions in early grades seem to offer the best hope yet advanced ... How much more evidence do leaders need before they apply these strong findings to help improve schooling?
C. Achilles, paper to the North Carolina Association for Research in Education, 1993
WHAT PARENTS SAY
Jane Bowe, mother of two boys aged eight and six and parent governor of West Pennard Church of England Voluntary Controlled primary school in Somerset:
She and her husband, Martin, have moved their elder son to a private school where class sizes are smaller. Her younger son remains at the primary school where she is a governor. The school faces a loss of around pounds 17,000, the cost of a teacher.
"This is a very good school, but apart from the reception year, which we peg at 28, classes sizes are around the 31 to 32 mark. If we lost a teacher, they would be 35 or 36.
"My elder boy could not cope in a large class. He is a very able little boy and he was choosing to cruise. The teachers work so hard, but there is only so much attention you can give to any child in a class that size.
"My parents were both headteachers in the state sector and it went against the grain to take him out of the state sector. Now he is in a class of 22 and has more individual attention. He can't get away with sitting looking out of the window. There is a tremendous difference in the kind of work he is producing and he is happier, too."
David Long, father of a 10-year-old and 12-year-old in Frideswide, an Oxford middle school:
His children's school faces the loss of three or four teachers because of budget cuts. His former tutor at Oxford was John Patten, Gillian Shephard's predecessor, and he is one of the leaders of a local campaign against the education cuts.
"The smaller the group, the more opportunity there is for dialogue between the pupils and the teacher. When my children were in first school and classes were 30 or more, I would spend an hour a week helping with a maths group along with a learning assistant and the teacher. The class would be split into three groups of similar ability, children on tables with three adults rotating round them addressing individual needs. There are bound to be fewer gaps if you work with smaller groups. I was an Oxford undergraduate who was taught at times either one to one or one to two. The benefits of that are immense."
Margaret Morrissey, national spokeswoman of the National Confederation of Parent- Teacher Associations and mother of two:
"My daughter started school in inner London in classes ranging from 35 to 37. My son was younger and was able to get into the nursery school of a school which had a starting class of 15. He was never in a class bigger than 21 in primary school. He went to university at 17. My daughter left school at 16 and took her A-levels later, eventually going to university at 22.
"I think she never recovered from the lack of individual attention at the beginning. She has picked herself up in the end but some of the other kids in her classes will never do that."
Mother of a six-year-old who is in a class of 28 in a Nottinghamshire primary school:
"Smaller classes undoubtedly make a difference. My little girl started school in a class of 32. When they could break them up into groups of six to 10 with a teacher and the nursery teacher, the children were more attentive. They had someone in to help with maths who worked with six children at a time. Rebecca was so confident with her maths; she is less so now."
Parent quoted in research by Neville Bennett, of the University of Exeter: "Any half-wit should realise that increasing class size is detrimental to a child's education."Reuse content