Class size has historically been a contentious issue for parents, schools, and policymakers. There has been a lot of research on the topic, but in many cases the wrong questions have been asked. Taking a look at the evidence, the authors of a new book argue that class size does indeed matter, but why and how are highly complex questions.

There has been considerable debate globally about the influence of class size on teaching and learning. In England, a maximum class size of 30 students applies only to 5- to 7-year-olds. In the case of older children, there is no limit to the number of students in a class. With average class sizes increasing in most England constituencies between 2010 and 2019, reducing that trend is seen as a top priority by some teachers. But what does the evidence say?

What is the impact of class size on children’s learning?

An evaluation of six meta-analyses by the Education Endowment Foundation shows that reducing class sizes produces a ‘moderate impact’, roughly equivalent to three months’ additional progress in average pupil attainment over a year. The clearest effects are seen when the class size is reduced substantially – to fewer than 20 or even 15 students.

“The clearest effects are seen when the class size is reduced substantially.”

For a deeper dive into the evidence, I turned to a new open access book by Peter Blatchford and Anthony Russell called Rethinking Class Size. The book brings together their reading of the literature, their own extensive research, and their experiences in the classroom. The authors argue that class size does in fact matter, but that the topic has not typically been researched and thought about in the most useful way.

According to Blatchford and Russell, we should move away from thinking of class size reduction as an intervention. In reality, there is no simple link between class size and attainment. There can never be a meaningful ‘effect’ of class size because class size has complex associations with everything else that happens in the classroom. Similarly, we should not assume that reducing class size is an easy solution to difficult problems in the classroom.

“There is no simple link between class size and attainment.”

So, class size is a complicated issue. Simply looking at the impact of class size on academic attainment misses important information about what is happening in the classroom. In smaller classes, teachers can give more individual attention to students, tailor instruction more easily to different ability levels, monitor group work, and provide ongoing feedback. Administrative tasks are less demanding, as there is less marking to do and feedback is required for fewer students. Workload is an important factor in teacher wellbeing, so there are knock-on effects for staff satisfaction. Students report better relationships with peers and teachers, as well as increased participation in classroom activities and improved wellbeing.

Who gains the most from smaller classes?

Blatchford and Russell identify two groups of students who are likely to gain the most from smaller classes. The first group is younger students. Despite the 30 student limit in the lowest years of school, class sizes are typically larger at primary school than secondary school in England. The authors argue that primary classes should be reduced to match the size of secondary-school classes. The authors also note that lower attaining pupils and those with special educational needs and disabilities are particularly disadvantaged when class sizes increase – they receive less attention from the teacher and more negative teacher comments. In a large class with students of different levels, it can be a challenge for teachers to differentiate work in a way that meets the needs of all. Teaching assistants may be deployed, but they can have a negative impact if the school fails to prepare them adequately.

“Lower attaining pupils and those with special educational needs and disabilities are particularly disadvantaged when class sizes increase.”

Class size is obviously a complex issue. When it comes to general improvement in academic attainment, simply reducing class size is no panacea. Class size has multiple impacts, and considerable research remains to be done. It seems clear, however, that certain pupils – and teachers – would benefit from smaller classes. It is time to move beyond thinking about class size in terms of a single cause impacting academic achievement, or a single solution to problems in the classroom. As Blatchford and Russell’s book urges, let’s rethink class size and embrace the complexity of the evidence.

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