Class size and attainment: a summary of results from the CSPAR project
There was a clear effect of class size on children’s academic attainment over the first year of school (4/5 years), in both literacy and mathematics, even after adjusting for other possible confounding factors. The effect sizes were comparable to that reported by the STAR project. The relationship between class size and first (reception) year progress in literacy varied for pupils of differing baseline attainment (bottom 25%, middle 50% and top 25%). As class size got smaller, there was a statistically significant increase in attainment for all three groups, though the effect was larger for pupils with lower baseline attainment. Effects were still evident on literacy progress at the end of the second year of school (Year 1), though by the end of the third year the effects were not clear. There were no clear longer-term effects of class size differences on mathematics achievement. Though this finding indicates that the early benefits ‘wash out’ after two years in school, there were no restrictions in terms of which size of class they moved to from year to year. In other results it was also found that moving to a class of a different size, especially a larger class, had a negative ‘disruption’ effect on students’ academic progress.
Key potentially confounding variables were controlled for and one can be fairly confident that results reveal an independent effect of class size on pupil attainment – i.e., that smaller classes lead to higher academic attainment - over and above other variables.
Class size and classroom processes: a summary of results from the CSPAR project
In the CSPAR, large-scale systematic observation studies conducted when pupils were 4/5 years and 10/11 years showed that at both ages, though there was a heavy reliance on whole class teaching and individual work, pupils in small classes were more likely to experience one-to-one teaching and were more often the focus of a teacher’s attention. We concluded that in smaller classes there was more likelihood of what we call ‘Teacher support for learning’, a main feature of which was individualized teaching in small classes.
In the follow up DISS study, this finding was replicated, and, moreover, it was found to continue into secondary schools. The connection between class size and individualization therefore seems a robust finding.
There is a good deal of evidence that pupil inattentiveness in class has negative effects on pupils' achievement . In the DISS study we examined class size and pupil attentiveness across both primary and secondary years. Interestingly, there was a statistical interaction between class size and pupil attainment group (i.e., whether the pupil is from high, medium or low attainment groups) on pupil behaviour; low attaining pupils were far more likely to be off task in larger classes, and, conversely, more likely to benefit from smaller classes, in comparison to middle and high attaining pupils.
Reviews of research on class size
There have been a number of reviews written by Peter Blatchford and colleagues, including a major review commissioned by the American Psychological Association:
Blatchford, P. (2011) Three generations of research on class size effects. Chapter in: The American Psychological Association (APA) Educational Psychology Handbook. Vol. 2 Individual Differences and Cultural and Contextual Factors. pp 529-554. Editors-in-Chief Karen R. Harris, Steven Graham and Timothy Urdan. American Psychological Association: Washington, DC.
And a shorter review:
Blatchford, P. (2012) Class size: is small better? In Adey, P and Dillon, J. (Eds) Bad Education: Debunking Myths in Education. Open University Press.
Blatchford, P. and Lai, K.C. (2010) Class size: arguments and evidence. In Barry McGraw, Eva Baker and Penelope P. Peterson (Eds.) International Encyclopedia of Education. 3rd Edition. Elsevier
Blatchford, P., Hallam, S., Ireson, J., and Kutnick, P. with Creech, A (2010) Classes, groups and transitions: structures for learning and teaching. In Robin Alexander (Ed.) The Cambridge Primary Review Research Surveys. Routledge
Blatchford, P. (2008) Class size. In Anderman, E.M. and Anderman, L. (Eds.) Psychology of Classroom Learning: An Encyclopedia. Farmington Hills, MI: Thomson Gale
Blatchford, P., and Catchpole, G. (2003) Class size and classroom processes. In J.P.Keeves., and R. Watanabe (Eds.) International Handbook of Educational Research in the Asia-Pacific Region. pp741-754. Dordrecht: Kluwer,
The following early reviews were the basis of the rationale for the CSPAR study and its design:
Blatchford, P., Goldstein, H. & Mortimore, P. (1998). Research on class size effects: a critique of methods and a way forward. International Journal of Educational Research, 29, 691-710.
Goldstein, H. & Blatchford, P. (1998). Class size and educational achievement: a review of methodology with particular reference to study design. British Educational Research Journal, 24 3, 255-268.
Goldstein, H. & Blatchford, P. (1997). Class size and educational achievement: a methodological review. Report commissioned by UNESCO.
Blatchford, P. & Mortimore, P. (1994). The issue of class size in schools: what can we learn from research? Oxford Review of Education, 20 4, 411-428.
Mortimore, P. & Blatchford, P. (1993). The issue of Class Size. National Commission on Education, Briefing No. 12, March.
A full list of publications is here: (link to 'Publications' section of the website)
Class size and pupil attainment: Sources
The most comprehensive description of the KS1 (5-7 years) part of the research is in the book: Blatchford, P. (2003) The Class Size Debate: Is Small Better? Maidenhead: Open University Press
Findings from the CSPAR KS1 study were reported in this Journal paper:
Blatchford, P., Bassett, P., Goldstein, H., and Martin. C. (2003) Are class size differences related to pupils’ educational progress and classroom processes? Findings from the Institute of Education Class Size Study of children aged 5-7 Years. British Educational Research Journal , 29, 5, 709-730. Special Issue ‘In Praise of Educational Research’, Guest Editors: S. Gorrard, C. Taylor and K. Roberts
A detailed analysis of effects on attainment just for the first (reception) year of schooling is in:
Blatchford, P., Goldstein, H., Martin, C. & Browne, W. (2002). A study of class size effects in English school reception year classes. British Educational Research Journal. Vol. 28, No. 2, pp. 170-187.
Class size and classroom processes: Sources
Findings on the effect of class size and classroom processes when pupils were in KS1 (5-7 years) can be found in:
Blatchford, P. (2003) A systematic observational study of teachers' and pupils' behaviour in large and small classes. Learning and Instruction, 13,6, 569-595
And: Blatchford, P., & Martin, C. (1998) ‘The Effects of Class Size on Classroom Processes: “It’s a bit like a treadmill - working hard and getting nowhere fast!”. British Journal of Educational Studies, Vol. 46, No. 2, 118-137.
Findings on the effect of class size and classroom processes when pupils were aged 10/11 years:
Blatchford, P., Bassett, P., and Brown, P. (2005) Teachers’ and pupils’ behaviour in large and small classes: a systematic observation study of pupils aged 10/11 years. Journal of Educational Psychology , 97,3, 454-467
Findings on the effects of class size on teaching can be found in:
Blatchford, P., Moriarty, V., Edmonds, S., & Martin, C. (2002). Relationships between class size and teaching: a multi-method analysis of English infant schools. American Educational Research Journal. Spring 2002 Vol. 39, No. 1, pp 101-132.
And in: Blatchford, P., Russell, A., Bassett, P., Brown, P., and Martin, C. (2007) The effect of class size on the teaching of pupils aged 7-11 years. School Effectiveness and Improvement , 18, 2, June, 147-172
Findings on the relationships between class size and pupil attentiveness and peer relations can be found in:
Blatchford, P., Edmonds, S., & Martin, C. (2003). Class Size, pupil attentiveness and peer relations. British Journal of Educational Psychology, 73, 15-36.
Findings on class size and the number and size of within class groupings can be found in:
Blatchford, P., Baines, E., Kutnick, P., & Martin, C. (2001). Classroom contexts: connections between class size and within class grouping. British Journal of Educational Psychology, 71, 2, 283-302.