Small class size has at best a small effect on academic achievement

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

One thought on “Small class size has at best a small effect on academic achievement”

  1. This is an interesting study on the effect of class size on academic achievement. Common sense seems to suggest that the smaller the class size the better the learners achievement and have often given a comparison between the class sizes in high income and low income countries. This study provides more insights on the subject but also leaves room for further investigation especially on the effect of class size on maths achievement which could create some doubts (would you expect a lesser academic achievement of a child from a smaller class in maths compared to one from a bigger class with associated support challenges!).

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