Literacy standards: Link to class size

Professor Peter Blatchford, leader of the research team, said: "Although these findings seem obvious to most teachers and parents, research evidence to date has not borne them out.

"Our study not only confirms the link between class size and academic progress - it also shows that what goes on in the classroom is affected by the number of children in a class."

For their research, the team studied more than 10,000 children in more than 300 state schools in 13 education authorities in the UK.

They found that children in smaller classes in their first year of school improved measurably in literacy and maths tests.

They also found that achievement in literacy decreased as class size rose from about 15 to about 30, although in maths there was little effect on progress in classes with more than 25 pupils.

'Clear effect'

The research report suggests that in literacy, children who started school as low achievers benefited most from smaller classes, with the most important benefits occurring when class sizes fell below 25.

This week the Liberal Democrats said that, if elected to government, they would deliver primary school class sizes of no more than 25 pupils on average.

Professor Harvey Goldstein, a member of the project team, said: "Our analyses show that class size has a clear effect, both before and after adjusting for other possible influences, such as disadvantage.

"A drop in class size from 25 to 15 leads to a gain in literacy of about one year's achievement for the bottom 25%, and about five months' for the rest."

Reading aloud

Unsurprisingly, researchers found that teachers in smaller classes responded to pupils more quickly and effectively, and knew more about individual pupils, while children in larger classes were less likely to be heard reading aloud.

Pupils in larger classes were also more easily distracted, and doing things other than their set work.

Prof Blatchford said: "Teaching quality is obviously vital, but teachers do not operate in a vacuum. They have to adapt to the classroom context, including the number of children.

"The effects of class size are complex, as seen by our discovery about social relationships.

"We would hope that these findings will initiate a drive to find ways to maximise the benefits of having fewer children in a class."

'Sustained interaction'

John Bangs, head of education for the National Union of Teachers, called the study "positive", but said the findings were "not surprising".

John Bangs: "Positive study"

"We did our own study with Leicester University and we found that where you do have smaller classes you get teachers able to spend much more time in what's called critical questioning with pupils - the interaction between the pupil and the teacher is much more sustained.

"With smaller groups the teacher is able both to engage the whole group in conversation and discussion about what's being done, but then the teacher can actively concentrate on an individal pupil, and talk for a long time, and ask very critical questions about what the pupil understands.

"You can't do that in a large class - you're constantly involved in classroom management."

'It depends...'

Mr Bangs said he took the suggestion that children in classes of fewer than 20 pupils were more aggressive towards each other "with a pinch of salt".

"It really does depend on the nature of the pupil and it also depends on what's being taught," he said.

The NUT is calling on the leading political parties to include a statutory requirement to reduce class sizes for all age groups in their election manifestos.

The Shadow Education Secretary, Theresa May MP, said: "This study proves that the government's arbitrary class size target of 30 is completely pointless.

"Despite all of Labour's measures, children are no better off."

What Labour had done, she said, was to reduce parents' choice of school for their children - by limiting the numbers who could attend popular schools.

The Tories say they would allow head teachers and governors to manage their schools as they saw fit.