A major international study is to investigate the impact of class size on teacher effectiveness - and how teaching techniques vary in response to changes in the number of pupils.

Researchers in five countries are taking part in the project, which comes against a background of increasing debate about the effect of class size on student achievement.

Earlier this month, Ed Miliband said a Labour government would limit infant class sizes to 30 pupils, echoing a pledge made by Tony Blair in the run-up to the 1997 election.

The number of infants who are in classes of 30-plus has more than doubled over the past five years.

But OECD figures show that some countries and regions that perform well in international comparison tests - such as Shanghai and Hong Kong - have higher than average class sizes.

Professor Peter Blatchford of the UCL Institute of Education, who is directing the study, believes previous research focusing on the link with student achievement ignored the effect of class size on teaching techniques. This study aims to come up with ways for teachers to make the most of smaller or larger classes.

Another strand of research showing that teachers tend not to tailor their approach to the number of pupils could help to explain the relatively modest impact of class size on student outcomes, according to Professor Blatchford.

“I think the most important educational questions are about how to adapt teaching to make the most of having fewer (or more) pupils in a class,” he writes in a blog for the IoE.

Among the areas that researchers will examine is the impact of collaborative group work, which could benefit from smaller classes, he adds.

The study is funded by the Leverhulme Trust and involves researchers in the UK, France, China, Hong Kong and the US.

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Increase class sizes to free up resources for teacher training, says leading academic - 4 November 2014

China’s poorest children outperform UK’s middle class in international maths tests - 18 February 2014