Background to the project







There has been a vigorous debate about class sizes in schools. On one side of the debate are the enthusiasts who feel very strongly that smaller classes lead to better teaching and more effective learning. On the other side of the debate are the sceptics who argue that the evidence for the efficacy of class size reductions is in doubt and that there are likely to be other more cost effective strategies for improving educational standards.

At the time this study originated, there was a widely perceived problem of large classes at primary level in the UK. Unusually, in comparison with many other countries, class sizes are larger on average in primary than in secondary schools. As an example, in 1996 the average class sizes in England at primary was 27.5 and at secondary level 21.9. This seemed to us to turn on its head what was more sensible educationally – that is, younger children need more support from their teachers. Despite the cap of 30 on class sizes at reception and Key Stage 1 introduced by the Labour Government, there is still wide variation in class sizes and they are still larger than those in secondary schools.

In visits to schools it was clear that the overwhelming professional judgement of teachers was that smaller classes allow more effective and flexible teaching and the potential for more effective learning. Suprisingly, there had been little research conducted on this topic in the UK, and, oddly, that which existed tended to show if anything that children did better academically as class size increased.

Therefore, to answer these research questions the Class Size Research project was instigated, and started in 1996. Initially this was funded by Local Authorities, in conjunction with the Institute of Education. Later on, the research has been funded by a grant from the DfES (now DCSF) and the ESRC.

The project had two main aims:

  • to establish whether class size differences and pupil adult ratios affect  pupils' academic achievement. 
  • to study connections between class size and classroom processes which might explain any differences in attainment that we found. We looked at several main processes: within class grouping practices, teaching, individual support for reading, pupil concentration and peer relations.
The Key Stage 1 (KS1) study involved tracking over 10,000 pupils in over 500 classes in over 300 schools from school entry (at 4/5 years) to the end of KS1 (at 6/7 years), that is, over their first three years of school. It featured an impressive multi-method approach that involved the collection of information on a range of factors including: class size, the number of staff and other adults in the class, information on teacher and pupil behaviour in class from systematic classroom observations and teacher ratings of individual pupils, teacher estimates of time in different curriculum areas and activities, end-of-year reports by teachers of effects of class size differences, and detailed case studies of individual classrooms. Deliberately, the study set out to integrate quantitative and qualitative research.

In contrast to the famous USA STAR project, it was conducted using a non-experimental design; in other words, rather than assign children and teachers to different class sizes, we measured the effects of natural variations in class size. We did this with a longitudinal follow-up study of children from school entry, and employed sophisticated multilevel regression statistical analyses in order to determine effects of class size controlling for other factors, such as pupil prior attainment.

The aim was to provide an integrated and comprehensive account of how class size affects classroom learning and behaviour.

Subsequently the study was extended into Key Stage 2 (7-11 years), following the progress of many of the same pupils from Key Stage 1, together with a collection of new pupils.

In a later study – the Deployment and Impact of Support Staff (DISS) project - we were able to examine the effects of class size on teacher pupil interaction and pupil classroom engagement across both primary and secondary sectors. A paper reporting results on this, including the benefits of small classes for low attaining pupils, can be downloaded here.