CHILDREN born in summer have poorer literacy skills at primary school than those with birthdays in winter, new research shows.

Tests on seven-year-olds in Northern Ireland have found that those born between May 1 and August 31 performed worst in spelling and reading tasks, while November and December babies had the highest scores.

The results were not due to the summer-born children being the youngest in their class, because the cut-off point for school entry in Northern Ireland is different from the Republic of Ireland and England. Pupils must be four-years-old by July 1 to start school in September. This means those born in July and August are actually the oldest in their year.

Martin McPhillips, a psychologist at Queen’s University, Belfast and one of the study’s authors, said: “On spelling, the summer-born children, irrespective of whether they were the oldest or youngest in the year group, did the worst. The July/August ones are as weak as May/June ones. There seems to be some biological weakness in children born in the summer months.”

Previous research in England showed the youngest children performed less well, but because of the cut-off point it was not possible to work out whether this was just due to them being less mature or because they were born in summer. Northern Ireland was the perfect place to do the research, because the cut-off is in the middle of the summer. This means summer-born children are both the oldest and youngest in the classes.

“We have been able to show there is an obvious biological disadvantage for summer-born children,” McPhillips said.

But not everybody is so sure. Mary O’Rourke, a former education minister who was born on May 31, said: “Thankfully I have terrific literacy, and have had from the beginning. My two sons, who were born in August and September, have proven to be extremely literate. I think we all gobbled books in the early years, so we disprove the theory.”

In one type of reading test, children born in November and December scored 53% higher than May/June pupils and 35% more than July/August ones. The winter-birth students were 13% to 16% better at spelling than summer ones. The effect seems to level out as children go through school. By age nine it had started to fade and among 11-year-olds it had been overridden.

The research, published in the British Journal of Educational Psychology, involved 1,124 children in years three, five and seven in 13 primary schools. It cites other studies finding that children born in summer were at a disadvantage. In Austria and Denmark a study found people born between October and December live longer than those born between April and June.

Research in the UK has found a higher risk of suicide among people born in April, May and June; the lowest proportion had autumn and early winter birthdays. Such studies suggest seasonal factors may affect the womb or early months of life that have long-term implications for both physical and psychological wellbeing.

McPhillips said: “Some people have suggested that this is because of the pregnancy running across different months of the year. If you are born in May, June, July or August, the pregnancy will have run across the winter months. If you are born in November, December or January, it won’t. You’ve had a pregnancy that’s been free of bugs and viruses that dominate the winter months. Your diet may be better across the summer months, and there is more sunlight so more vitamins.”

In the republic, the cut-off point for school entry is September 1, so children with birthdays in summer are the youngest in class. Ireland’s compulsory school-starting age is six, and parents can choose to send their children to school at four or five. Children born in summer in the republic may benefit from starting school at five instead of four, said McPhillips.

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