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The bar graph plots the average number of students in each class in elementary schools and middle schools in 6 countries relative to the world average in 2006.

Overall, South Korean schools had the largest number of students per class, 34 versus 36, followed by Japanese schools (29 versus 34). Schools in the UK and Mexico had wide gaps between the average size of a class in primary school and secondary school.

Denmark and Iceland were quite similar, with average size class in elementary varied in a narrow gap between 25 and 23, and Secondary school, 21 and 20 respectively. Schools in the UK had the smallest size class in Secondary schools, approximately 18 pupils per class, almost half of the average size class in South Korea and Japan. Similarly, Mexico had the smallest size class in primary school, 20 pupils per class, nearly half of that in South Korea. The world average size class had less than 20 pupils per class as compared with South Korea in both types of schools, and 10 pupils less in primary schools as compared with Japan.