A study suggests closing schools during a flu pandemic might slow the spread to a degree but likely won't dramatically lower the overall number of cases.

The modelling study, by British and French researchers, shows school closures might cut the number of cases by between 13 and 17 per cent and potentially less if kids congregated elsewhere.

Some studies have suggested a much greater impact from school closures and pandemic planners are considering recommending the move based on the notion that children are very efficient spreaders of influenza.

This study, published in the journal Nature, uses data from France to analyze the impact of school holidays on the transmission of flu.

Mathematical models constructed using those data show holidays slow transmission among children but don't have a detectable effect on the patterns of contact between adults.

The authors say school closures might still make sense in a severe pandemic but people should temper their expectations of how useful this tool would actually be in cutting cases and deaths.