Can Your Birthday Really Determine Your Future Success? New Research Says Yes

There are a million variables that duke it out to determine whether a kid is going to be “good” at school or “bad” at it, but researchers have gotten closer to understanding at least one of them.

In a new paper, academics from the University of Valencia and the Paris School of Economics compared prospective college students' entrance exam scores, and found that those born at the beginning of the academic year (September and October for many American schools) performed better than those born at the end of it (“summer birthdays” in the U.S).

But here’s where it gets weird. Girl students, the researchers found, are far more likely to be impacted by this phenomenon than boys — and for a much longer period.

What’s going on here, exactly?

Pedro Javier Soria-Espín, a graduate student at the Paris School of Economics and the paper’s coauthor, says an early cognitive imbalance is partially to blame. If you’re a six-year-old kid tossed into a first-grade classroom with students who are 9, 10, or 11 months older than you, you’re probably getting the short end of the academic stick. His study focused on European students, but this is true across many cultures — particularly the U.S. (In 2017, a team of economists found that the youngest Florida public school students had the lowest grades. Another study from 2015 shows these students are nearly 80% more likely to repeat a grade).

Past research also shows that girls are more affected by things like social exclusion and classroom norms, and that males of every age tend to have higher self-esteem than females (shoutout @thepatriarchy!). So it makes sense that girls would internalize the confidence annihilator that comes with, say, always being the last student to finish her math homework, or the only one who has to skip recess to practice her cursive handwriting, to a greater degree than boys do.

In the University of Valencia study, older female high school seniors vying for a spot at the university scored about one point higher on their entrance exams than their younger female peers. The difference in test scores among male students was so low, on the other hand, it had “no statistical significance.”

A one-point difference might not seem like a lot, but when you consider how heavily things like ACT and SAT scores are weighted in college admissions decisions—and how mere points can make the difference between getting into your “top” program, or getting a hefty scholarship, (especially in ultra-competitive fields like medicine and engineering)—the research is hard to ignore.

“We observe in the margins, where people are fighting for decimals in entry grades, older girls get this extra boost,” Soria-Espín says. “This is creating a sort of unintended inequality ... even among top degrees.”

Being the youngest boy in class comes with hurdles too: Research has shown that the majority of male professional athletes were usually the oldest students in their classes growing up. But while having a summer birthday might sink the hoop dreams of teenage boys nationwide, the implications for girls are more deeply entrenched.

Older girls tend to have higher self-confidence, which is rewarded in perpetuity. “They get better opportunities, and better promotions, because of things they’ve internalized since the beginning of their scholastic life," Soria-Espín says.

The good news, according to the researcher—who, along with yours truly, has a late birthday himself—is that this learning gap seems to level out eventually. In the study, he and coauthor Pilar Beneito, a professor of Economics at the University of Valencia, also looked at accepted first-year college students’ GPAs, and found that birth month had less of a pronounced effect.

Still, for American students, at least, that’s after a decade and a half of K-12 education — where state-mandated standardized tests and other imperfect methods of academic evaluation have already guided students into big decisions about where their talents lie — and what kind of career they’re best suited for.

Good education policy could address this, Soria-Espín says. Schools could restructure classes so that elementary-age classmates only have a six-months gap between the youngest and oldest students. Or they could just stop grading six-, seven-, and eight-year-olds altogether, and move to a rewards system that doesn’t stamp “A student” or “C student” on a kid’s forehead before her first book report.

Until then, Soria-Espín says, the best hope for us August birthdays is what’s always given kids a leg up: Compassionate parents and teachers who are patient enough to walk us through our hangups until we catch up with the rest of the class — be they math equations, cursive handwriting, or otherwise.

“Early interventions can bridge this gap,” Soria-Espín says. “And being comprehensive and understanding with younger students can improve the system.”

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