Kids born August are more likely to have to poor academic performance, receive an ADHD diagnosis, and get into trouble with the law.

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Say your child was born in August, and your school district's cut-off date is September 1. The timing may spark some worries: Will my kid struggle more in school due to her young age? Will she be as socially mature as the other kids in her grade who were born earlier in the year?

And it turns out, some of these worries are valid. An August 2017 study reported a link between behavior, cognitive ability, and school starting age. Specifically, children born in August who weren’t held back (redshirted) had worse behavior and performed more poorly in school than their older peers.

The study, which was published in the National Bureau of Economic Research, tracked students between the ages of 6 and 15 in public schools. The children lived in Florida, where a cut-off date of September 1 determines when you’ll start school.

Compared with students who had August birthdays, the September-born students were 2.1% more likely to attend college – and 3.3% more likely to graduate college. Similarly, the older students were significantly less likely (15.4%) get into trouble with the law as minors.

“If you are the oldest in your class, your brain has had more time to develop than all the other kids. So, while an August baby may have the same IQ as a September baby, their brain hasn’t had the same opportunity to grow and mature,” Katherine Firestone, founder of the Fireborn Institute, told People. “So, the September baby is socially adept and his brain is ready to learn to read, but the August baby is 11 months behind and may not yet be ready.”

A Link Between School Start Date and ADHD

To add to the bad news, a May 2016 study by researchers in Taiwan, published in the Journal of Pediatrics, revealed that kids with August birthdays are more likely to be given an ADHD diagnosis.

Researchers studied data from more than 370,000 children between the ages of 4 and 17. About 2.8 percent of preschool and elementary school boys born in September were diagnosed with ADHD, compared with 4.5 percent of boys born in August. For girls the numbers were not quite as dramatic, rising from 0.7 percent to 1.2 percent.

As for why this is happening, researchers explain that an ADHD diagnosis is subjective. So when a child is immature compared to other children in the same grade, they are more likely to be inattentive, impulsive, and hyperactive, which in turn may lead a teacher to refer them to a doctor for evaluation.

Adolescents, however, were less likely to be diagnosed with ADHD if they were younger than their peers. This, study author Mu-Hong Chen wrote, "may imply that increasing age and maturity lessens the impact of birth month on ADHD diagnoses."

The study underscores the importance of considering the age of a child within a grade before diagnosing ADHD and prescribing medications like Adderall and Ritalin. Hopefully, this will help prevent future ADHD misdiagnoses down the road.