Reducing class size is often suggested as a way of improving pupil performance. However evidence from a new Campbell systematic review suggests that reducing class size has at best only a very small effect.
The review summarises findings from relevant studies that measured the effects of class size on academic achievement. A total of 127 studies were analysed, including 45 studies that used data from the US Student Teacher Achievement Ratio (STAR) programme that reduced class sizes substantially in kindergarten to grade 3 (Years 1 to Year 4). However only ten studies, including four of the STAR programme, could be included in the meta-analysis.
Their analysis focused on effects on maths and reading and found a small positive effect of reducing class size on pupils’ reading achievement and a negative, but statistically insignificant, effect on maths. For reading, the weighted average effect size was +0.11, and the weighted average effect size for maths was -0.03.
For the four studies using data from the STAR programme, the researchers found a positive effect of smaller class sizes for both reading and maths. However, the average effect sizes were still very small and do not change the overall finding.
Source: Small class sizes for improving student achievement in primary and secondary schools: a systematic review (October 2018), Campbell Systematic Reviews 2018:10