Teaching children from different age brackets in the same class has a negative effect on girls, but little or no impact on boys, a study of Irish primary schools has found.

Girls taught with older children had lower reading and maths test scores than girls in single-grade classes.

They also had poorer behaviour and were more negative about their academic abilities and popularity than girls taught in their year group.

In contrast, boys' academic performance was unaffected, albeit those taught in classes with younger peers tended to have poorer behaviour – what researcher Dr Emer Smyth describes as "a messing effect".

Her study, compiled with fellow ESRI researcher Amanda Quail, was published in the international journal Teaching and Teacher Education, and draws on data from more than 8,500 nine-year-olds in the Growing Up in Ireland study.

A third of Irish primary school children are taught in “multigrade classes”, where two or more age groups in a small school are pooled under one teacher. Despite this, there has been very little research domestically or internationally on the subject, the authors note.

Dr Smyth said the data showed there was no major shift in academic performance overall but what effects there were had been “largely driven by the girl factor”.

Explaining this, the authors say: “It appears girls make more comparisons with their peers than boys and, as a result feel, more negative about their abilities. This negative view of their abilities may then affect their actual academic performance. There certainly is a challenge for teachers to manage the gender mix as well as the age mix, so girls don’t miss out.”