Skip to navigationSkip to content

A new ADHD study offers yet another reason to stop sending kids to school early

child on swing
Reuters/Kai Pfaffenbach
Sometimes kids just need a little more time to catch up.
By Jenny Anderson
Published Last updated This article is more than 2 years old.

Kids who start school at a younger age than their peers often have a tough time. When you’ve been on planet Earth for almost a year less than your fellow kindergartners, you’re bound to be less mature, more energetic, and less able to pay attention for long periods of time.

A new study published by Harvard Medical School researchers in The New England Journal of Medicine shows that kids who go to school early face another risk. Among a large sample of kids in US states with a Sept. 1 cutoff date for school enrollment, children born in August were 34% more likely to receive an ADHD diagnosis and treatment compared to their older classmates.

“Our findings suggest the possibility that large numbers of kids are being over-diagnosed and overtreated for ADHD because they happen to be relatively immature compared to their older classmates in the early years of elementary school,” lead author Timothy Layton, assistant professor of health care policy in the Blavatnik Institute at Harvard Medical School said in a statement.

Attention Deficit Hyperactivity Disorder (ADHD) is a chronic neurobiological disorder that affects the brain structurally and chemically, as well as the ways in which various parts of the brain communicate with one another. In boys, symptoms tend toward hyperactivity and inattention; in girls, ADHD symptoms can include a tendency toward daydreaming and trouble following instructions.

Rates of diagnosis of ADHD have doubled in the past 20 years. In 2016, 5% of children in the US were taking ADHD medication. Researchers attribute the spike in part to better recognition of the disorder and a genuine increase in the condition—but they also acknowledge that over-diagnosis has played a role, too.

The birthday effect

Here’s how a child’s birthday can shape their experience in school: Imagine you live in a school district with a Sept. 1 cutoff, meaning your child has to be five years old by Sept. 1 in order to start school. This means that a boy named Lucas, who turned five on Aug. 15, will enroll in the same class as Jack, who will turn six on Sept. 15.

Jack has been alive almost 20% longer than little Lucas. Developmentally, this is an eternity. He will likely have better self-control and be better equipped to do the things required in school, like sitting still and listening for long periods of time.

“As children grow older, small differences in age equalize and dissipate over time, but behaviorally speaking, the difference between a 6-year-old and a 7-year-old could be quite pronounced,” said study senior author Anupam Jena, an associate professor of Health Care Policy in the Blavatnik Institute at Harvard Medical School. What is normal for a five-year-old stands out as immature for six-year-olds.

The researchers from Harvard Medical School used the records of a large insurance database to follow more than 407,000 elementary school children born between 2007 and 2009, until the end of 2015. They compared the difference in ADHD diagnosis by birth month—August versus September.

In states that use Sept. 1 as a cutoff date for school enrollment, children born in August had a 30% greater chance of an ADHD diagnosis than children born in September, the analysis showed. These differences did not appear when when states had different cutoff dates.

Diagnosing ADHD is tricky: it requires parents, educators, administrators, and health-care providers to weigh in on whether a child needs help. The researchers also noted that many states now hold schools accountable for identifying ADHD, giving educators incentives to refer any child with symptoms for medical evaluation.

But teachers noted in comments to a New York Times article that it is sympathy that drives them to refer students for diagnosis.

“As a teacher, I don’t need kids to take meds to help me or make my day better,” one commenter wrote. “But I’ve seen medication lift the incredible burden of a condition a child cannot control from their small shoulders.”

Others pointed out that kids are held to wildly unrealistic standards these days—arguing that the real issue may not lie with teachers’ inclination to misread immaturity as ADHD, but with schools’ expectations about what a kindergartner should be able to do. One San Francisco teacher wrote:

“When I was in Kindergarten in the 1980s, it was a year of child-directed play and exploration. Now the four- and five-year-olds who enter my class are expected to end the year reading, completing symbolic addition and subtraction problems.”

The case for sending kids to school later

Other research suggests that enrolling kids early in school hurts them academically and emotionally. A 2017 working paper from researchers at the University of Toronto, Northwestern University, and University of Florida found that Florida kids with August birthdays —where the cutoff for starting kindergarten is Sept. 1—had worse elementary school test scores, were less likely to attend college, and more likely to be put in jail for a juvenile crime. This held true regardless of parents’ education level, income.

Holding kids back, or “red-shirting” as the practice is called in the US, also seems to have benefits. A 2015 study from Stanford University showed that Danish kids who postponed kindergarten for up to one year showed dramatically higher levels of self-control. Rates of inattention and hyperactivity were reduced by 73% by waiting. The author of that paper told Quartz that the effect was durable: rather than increasing over time, as expected, postponing school virtually eliminated the chance that an average kid at age 11 would have higher-than-normal scores of inattention or hyperactivity.“We were a bit surprised at how persistent the effect was,” said Thomas Dee, one of the co-authors and a Stanford Graduate School of Education professor.

Countries like Finland and Germany already have kids start school relatively late. Kids do not seem to fare worse later in life for the lost time, otherwise known as childhood: Finland scores well in international tests of 15-year-olds.

But currently, it the well-educated and wealthy parents of boys who are most likely to hold their kids back, creating further inequities in school. So what else is there to be done? One solution, according to the authors of the latest research, is to consider age carefully when weighing whether to refer a child for diagnosis. ”A child’s age relative to his or her peers in the same grade should be taken into consideration,” Jena said, “and the reasons for referral carefully examined.”

📬 Kick off each morning with coffee and the Daily Brief (BYO coffee).

By providing your email, you agree to the Quartz Privacy Policy.