Cutting down on class sizes is widely seen as a good way to advance classroom learning and student performance.
The idea, perhaps because of its simplicity, is even popular among politicians who campaign for improved quality in education.
But there is little support for this simple solution in studies on teacher-student rations and class sizes, according to economists Jon Marius Vaag Iversen and Hans Bonesrønning at the Norwegian University of Science and Technology
A study on Western European middle schools from 2005, for example, failed to show any differences between student performance in small and large classes. In a Norwegian study from 2008, no class-size effects were found in the performance of 15-year-old students.
“Many think these findings must be wrong,” says Bonesrønning. “They say a high teacher-student ratio will ‘obviously’ help students. But this is not necessarily the case.”
He says small classes can have positive effects, but it is still unclear why it works for some, and not for others.
“We’ve been hunting for situations where it actually helps,” he adds.
They found a few in one of their more recent studies, published in Education Economics.
Iversen and Bonesrønning followed pupils in small and large classes - 14-17 and 26-28 students per class - in Norwegian elementary schools for the first three grades.
At the start of the fourth grade the children took a nationwide test. Iversen and Bonesrønning compared the results of the two groups.
They found that positive effects of small class sizes were found on pupils whose parents have no formal education beyond secondary school, and pupils whose parents are divorced or live separately for other reasons.
“The positive effect of small class sizes is significant on these students,” Bonesrønning says. But there was, on average, no positive effect on other students.
Another group of students who benefit from trimmed down class sizes are hardworking girls. This is shown in one of their earlier studies of children in middle school.
“In middle school it’s the other way around,” he says. “For clever girls, small classes help as they’re often good at asking for help from teachers and parents.”
Boys in middle school, on the contrary, benefit little from a higher teacher-student ratio.
Bonesrønning thinks small class sizes have a positive effect when students are motivated for learning:
“I think this is why young students with disadvantaged backgrounds benefit from small classes."
Young pupils who are new to school are often eager to learn and improve, and they benefit from having many teachers around, according to Bonesrønning.
He says it is important to help these children while they’re young because poor students who experience defeat after defeat often give up, and at that point reducing the size of the class won’t help them.
“We have to think complementary, not compensatory.”
Bonesrønning says the notion of a widespread reduction of all school classes is problematic. It will necessarily add to the teachers' payrolls and burden the schools' budget, and the positive effect of smaller classes on students is, on average, not very big.
But it might be a useful tool for those who need it the most .
"We have to rethink what we can do for those who perform poorly in school. It’s a large group and we have to turn over every rock," Bonesrønning adds.
“For schools which recruit many students with disadvantaged backgrounds, having small classes the first years could be a good idea.”