Reduce the class size as a success story.
However, an international impact analysis shows unintended consequences: it often seems to mean lower pay for teachers, and there is not much evidence to show better results.
Reducing class size has been a popular policy in many countries, often supported by parents, politicians and teachers.
It was one of the big trends of the last decade.
Class sizes fell by 6% between 2006 and 2014 on average for lower secondary education in the members of the Organization for Economic Co-operation and Development (OECD).
These include more than 30 of the most developed countries, including most of Western Europe, Japan, Australia and the United States.
The expectation was that the smaller classes would mean a more personalized education with improvements in behavior and learning.
If all other factors are equal, the test results show that the smaller classes perform better.
But when it comes to investing in schools, there are always compensatory payments, and countries can only spend their money once.
When the education budget focuses on reducing class size, the numbers show that there are usually discounts elsewhere, especially with lower salary increases for teachers.
Throughout the education system, smaller classes lead to more classes, requiring more teachers to lead them, which in turn means higher costs.
Reducing class size can not only require more teachers, but also the establishment of more classrooms and the expansion of schools.
For the first time, the OECD has quantified these offsets, and their size is surprising.
To offset the cost of reducing the average class size of a single student, teachers’ salaries in more than half of the OECD countries would have to decrease by more than $ 3,000 (£ 2,320) annually.
In Switzerland and Germany, this would mean that wages in countries such as Austria, Norway, the United States, Finland, Australia, Spain and the Netherlands were more than $ 4,000 ($ 3,200) and more than $ 3,000 ( 2320 euros) is lowered.
Teacher salaries are an important part of school expenditure and any measure that will increase the number of teachers will soon have a major impact on the education budget.
The class size reduction offsets are displayed in the general image.
Secondary level teachers now receive only 88% of what other full-time employees earn.
If teachers’ salaries are not competitive, there are recruitment problems and the risk of leaving work to get jobs that are more rewarded.
Between 2005 and 2015, OECD teachers’ salaries increased by only 6% on average after inflation.
In one third of the OECD countries, the payment decreased in real terms.
There may be other national and economic factors affecting the pay of teachers, such as the financial crisis and public sector compensation.
However, to reduce class size, you must also take money that could have been spent elsewhere.
There might be other options. Teachers could work longer hours in class and reduce their preparation and non-teaching time. Or the lesson time could be shortened.
But finding the balance would have a high price. In some countries, this would mean that lesson time for students would have to be reduced by almost 70 hours a year to save the extra cost of hiring more teachers to reduce class size.
Is the reduced size of the class worth the cost?
There is no clear link between education systems with smaller classes and better learning.
The results of the last tests in Pisa show no correlation between average class sizes and achievements in science.
In fact, East Asian countries such as Singapore and China often top the rankings both in terms of performance and largest class size.
The results of science show, perhaps unexpectedly, higher scores for students in larger classes and in schools with a higher proportion of students and teachers.
Perhaps this is a matter of degree, and a significant reduction in class size may be required to have a positive impact.
However, it seems that powerful education systems always decide when they have to choose between smaller classes and teacher investment.
Of course, other political and economic choices could be made, such as increasing the funding for schools so that the number of teachers and their salaries can be increased.
Given that budgets are often limited, this study shows how spending options can lead to unforeseen outcomes.
Reducing class size is a costly exercise, so it makes sense to consider the benefits over other policy options.
If this was a financial decision, how would you get more for your money?
What about spending on raising teacher salaries, investing in teacher education, or changing the curriculum?
Could it reduce class size, which is considered a popular policy, at the expense of class quality?