When Lynn Stockwell’s children started attending a new elementary school 10 years ago, she noticed something unusual.
There was a preponderance of twins in the second grade at Reed Elementary.
Stockwell’s twin daughters, Audrey and Madison, are identical, but the majority of the twins at Reed, in the Ladue School District of suburban St. Louis, were fraternal.
She recalls the conversations at parent trivia nights and association meetings: “Oh, you’ve got twins,” she would say after meeting another mom. “And you’ve got twins, and you’ve got twins …”
A decade later, 12 pairs of twins are part of Ladue Horton Watkins High’s 2026 graduating class of 353 students. Another four students are twins whose siblings attend a different school.
So 28 of the 353 graduates are twins, which is roughly 1 in 12 students. The ratio in the U.S. overall is around 1 in 30, per the CDC.
“What is it about this age, and why are there so many in this class?” Stockwell asks. “This cohort of kids somehow found themselves in a similar place at a similar time.”
The coincidence may be rooted in the demographics of the district, which draws students from among the wealthiest ZIP codes in the state.
Professor Kimberly J. Saudino, of the Department of Psychological and Brain Sciences at Boston University, is the director of the Boston University Twin Project.
“Every so often, something like this happens,” Saudino says. It’s likely a combination of the proportion of parents using fertility treatments to conceive and advanced maternal age, which also increases the likelihood of having twins.
“Wealthier communities are more likely to have access to IVF,” she says. Women in higher socioeconomic groups and those with higher levels of education are also more likely to delay motherhood, according to U.S. fertility data.
The parents of the class of ’26 would have been conceiving in the mid-2000s, around the peak of the twin birth rate. The twin birth rate has been declining since 2014, partly due to a shift toward single embryo transfers in IVF. As the technology has improved, the incidence of multiples has declined.
Stockwell says the Ladue High twins have grown up together and formed friendships.
Sets of twins took pictures together before the prom. They hang out and socialize together. While some twins have their own separate friend groups, others overlap their social circles.
“Twins like to hang out with other twins,” Stockwell says.
Among the Ladue High twins, a few pairs will be going to the same college, while others are headed to different parts of the country.
Saudino’s research examines how much of a person’s temperament and personality is driven by genetics versus environment. Twin studies find that temperament similarities are more explained by genetics than a common family environment, she says.
While identical twins are nearly identical genetically, fraternal twins share no more genes than other full siblings do. And fraternal twins have been found to be temperamentally similar to regular siblings — not dramatically more so.
These twin clusters have popped up before. Last year, 15 sets of twins graduated from a Long Island high school, out of a class of about 500 students.
That’s still far from the most, according to Guinness World Records: That title belongs to New Trier High School in Winnetka, Illinois, which had 44 twin pairs and a set of triplets in the same academic year in 2017.
Aisha Sultan is a St. Louis-based journalist who studies parenting in the digital age while trying to keep up with her tech-savvy children. Find her on social media: @AishaS.