How old should our children be before they start a formal education? That's the question asked by new research from academics at Stanford University in the US, and it turns out that it might be better for our youngsters if they started school later – a whole year later in the case of the Danish children involved in the study.

Researchers used surveys filled out by tens of thousands of parents in Denmark, where youngsters typically start kindergarten at the age of six. Those who started aged seven showed lower levels of inattention and hyperactivity, factors known to be influential in improving self-regulation, which in turn is linked to academic achievement. The effects persisted up until age 11.

"We found that delaying kindergarten for one year reduced inattention and hyperactivity by 73 percent for an average child at age 11," explained Stanford's Thomas Dee in a press release.

"It virtually eliminated the probability that an average child at that age would have an 'abnormal', or higher-than-normal rating for the inattentive-hyperactive behavioural measure." Dee worked with Hans Henrik Sievertsen of the Danish National Centre for Social Research on the report.

Many developed nations are already choosing to push back the age at which children start pre-school, but this is one of the first major studies to look at the potential mental health implications associated with how kids might eventually perform at school.

Sievertsen told Quartz that the benefits of delaying the entry into kindergarten lasted a lot longer than he expected: in fact, waiting an extra year virtually eliminated the chance that, on average, by age 11 scores for hyperactivity and inattention would be above normal levels. In other words, there's a very high probability that the children who start aged seven are able to focus and pay attention to what's happening in the classroom by the time they reach 11.

For parents and authorities involved in the discussion over when to start kindergarten, it's a useful piece of evidence that shows a clear link to academic performance – the new study confirms the belief that those with lower inattention-hyperactivity ratings achieve higher school assessment scores. Data from 54,241 7-year-olds and 35,902 11-year-olds was used, and the same effects were noted across both genders.

"This is some of the most convincing evidence we've seen to support what parents and policymakers have already been doing – choosing to delay kindergarten entry," added Dee. "The study will give comfort to those who have [delayed entry], and for those who are making the decision, it'll give them a chance to consider the benefits."

However, the researchers were keen to point out that levels of inattention and hyperactivity are just two aspects of a child's development, and many other factors needed to be assessed too – not least the universally available and very highly rated pre-kindergarten facilities available in Denmark. Without these services, children may be better off starting kindergarten earlier, Dee said.