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Economist: The costs of shrinking classes outweigh the benefits


Reducing class sizes is not only very expensive, but also has only a limited impact on improving pupils' education. That's according to a large international study co-authored by Tomas Havranek of the SYRI National Institute. The researchers analysed a total of 62 peer-reviewed studies on the topic and found that class size matters surprisingly little. Havránek presented the results today at the SYRI Annual Conference in Prague's Karolinum.

The conclusion that smaller class sizes of 15 pupils are significantly better for children's education than regular class sizes of 25 pupils is used quite often in pedagogy, but the economist said it is "intuitive" rather than based on facts. "Also, pandemic funds in education have often been used to reduce class sizes, which is the case in the United States, but also in other countries," Havranek said.

The researchers were therefore interested in how much smaller classes actually help improve children's performance. The conclusions of the studies to date have conflicting results, with some showing no effect in reducing pupil numbers, and the literature as a whole is still waiting to be corrected for possible publication bias. A summary view is now provided by an analysis of a total of 62 studies. "It clearly shows that the class size effect is essentially null for most methodological approaches in the literature. The effect of class size is economically indistinguishable from zero," Havranek said.

This conclusion, he said, does not necessarily mean that class size reduction does not help students at all, or at least some of them. "But the potential benefits would have to be huge to justify the cost of across-the-board class size reduction, and it is doubtful that such large benefits will ever materialize. Until then, reducing class sizes in mainstream schools remains an evidence-based policy that is still being sought," Havranek said of the study, which has already passed its first round of peer review in the prestigious scientific journal Journal of Labor Economics.

The researchers subjected studies on the topic to a so-called meta-analysis, a statistical technique for reliably synthesizing research on a topic. There is a lot of published research, but the studies often disagree with each other because they differ in data and methods, and often in the quality of their treatment, which is the case with the topic of class size reduction. "This example also shows that results that are interesting and consistent with the prevailing intuition are easier to publish, so they appear in scientific journals more often than they should," Havránek explains. In practice, this complicates efforts to make decisions based on scientific facts. The results of meta-analyses thus help to correct entrenched scientific stereotypes.

Classs Size and Student Achievement: A Meta-Analysis


Prof. PhDr. Tomáš Havránek Ph.D.

Position: Senior researcher
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