Smaller classes are often seen as beneficial, because they allow teachers to focus more on the needs of individual students and reduce the amount of class time needed to deal with disruptions. Yet, while there is some evidence that smaller classes may benefit specific groups of students, such as those from disadvantaged backgrounds, overall evidence of the effect of class size on student performance is mixed.
Class size and student-teacher ratios
Class-size and student-teacher ratios vary strongly as countries weigh the trade-off between recruiting more teachers and investing into other elements of education systems.
Key messages
The ratio of students to teaching staff depends on how resources for education are allocated. Smaller student-teacher ratios often have to be weighed against measures such as higher salaries for teachers, investment in their professional development, greater investment in teaching technology or more widespread use of assistant teachers, whose salaries are often considerably lower than those of teachers.
Context
Class size varies strongly across countries
On average across OECD countries, there are 14 students for every teacher in primary education and 13 students per teacher in lower secondary education. The average class in a public primary school in OECD countries has 21 students as the number of teachers per school is generally higher than the number of classes per school. However, there are large differences across countries. In Costa Rica, the average class size in public institutions at primary level is 15 students, whereas it is 28 students in Chile. In many countries, the student-teacher ratio varies strongly across schools, with small schools often having well below 10 students per teacher, whereas larger schools may have more than 20 students per teacher.
Average student-teacher ratios have declined slightly over time
In most countries, student-teacher ratios change only slowly. Between 2013 and 2022, the average number of students per teacher has declined by 1.2 across OECD countries. However, greater changes can occur within countries as schools are affected by demographic trends at the regional or even local level.
