The impact of class size on academic performance


A meta-analysis of 127 studies carried out by Campbell Collaboration seeks to discover the effects of class size and its relation to academic performance.

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Decreasing the size of the class is an approach that has been tried, debated and analyzed over decades and yet, there is still no definitive conclusion about its effects on academic achievement. Reducing the volume of a class can be expensive, so it is important to consider what type of student could benefit from the change.

In theory, classes with fewer students allow teachers to meet the student needs individually and to adapt their lessons in order to provide a better learning experience. However, for this to happen, teachers must change the way they teach.

With this in mind, Campbell Collaboration analyzed 127 reports from 42 countries on the subject, although the majority were from K-12 classrooms in the United States. The authors of the meta-study focused on those studies that analyzed the effectiveness in the classroom and the support of teachers in regular-sized classes versus small-sized ones and how both options impact on cognitive performance.

Only ten of the 127 studies were used for the final analysis, and one-third of the publications came from the Tennessee Student-Teacher Achievement Ratio (STAR) in the 1980s, which analyze the reduction of the number of K-3 students. Of these studies, only four of the 45 met the inclusion criteria, and many were eliminated due to a lack of useful data.

Of the studies that did not use data from the STAR experiment, only six of the 82 studies could be integrated into the data synthesis because most were at risk of bias or did not provide sufficient information to calculate the size of the effects or standard error.

Of the studies analyzed, three reported a positive effect that favored the reduction of the class, and two indicated a negative impact and three concluded that the results were statistically non-significant. In addition, Campbell Collaboration analyzed the effect of class size in the specific case of reading and math lessons, in which it was found that fewer students have a positive impact on reading classes, while in math lessons, a negative or non-significant effect was reported.

The authors cannot rule out that reducing the size of classes can negatively affect some students, so it is essential to take into account the relationship between size, performance and the importance given by teachers and students. Therefore, it is crucial to investigate further the class-performance relationship, concludes the study, and how this factor influences the teaching work and student performance to determine whether investing in reducing the classroom is the best option.