(USA TODAY) -- Graduation will be doubly special for the Class of '14 at William Tennent High School, outside Philadelphia.
The 485 walkers include 14 sets of twins.
Diplomas will be handed June 20 out to five sets of male twins, two sets of female twins and seven sets of mixed twins, The Bucks County Courier Times reported Monday.
The Warminster, Pa., twins have distinguished themselves in academics. Eight sets are in the top 10% of their class, and two sets are in the top 5%.
The Tennent twins are "some of the best kids in the school," biology teacher Nicole Teeter said. "They're a really nice group. They're polite, they're active, they're involved in the community and the school."
No biggie, Mark Baner says.
"To us, this is no surprise. We've been doing it our whole life," said Baner, an honors student like his womb-mate sister, Cassie.
A 76% explosion in the twin birth rate from 1980 to 2009 -- from 18.9 to 33.3 per 1,000 births -- is generally attributed to fertility drugs and older mothers, who are more likely than younger women to have twins.
"I am reminded of this on a daily basis while walking through the hallways and wondering how did I just walk by the same student twice," principal Dennis Best said.