The Hanson School in Alexandria, S.D. is pretty small, with just 300 students in grades K-12.  But it might seem even smaller, since so many of its students look a lot alike.

"We've got three sets of triplets and seven sets of twins," said Superintendent Jim Bridge.  "For a little town like ours, it's kind of odd, but we're proud of it."

Bridge has no explanation for the trend, but admits it can be a bit confusing. "We've had one set of twins that graduated last year, and I couldn't tell them apart they looked so alike," he said.

This year there are two sets of twins in Hanson's kindergarten, a set of triplets in first grade, two sets of twins and a set of triplets in the third grade, and a set of twins in grades 7, 8 and 9.

Five sets of twins are identical or, at least, "Of the 7 sets of twins, 5 look amazingly close," said Bridge.

Kindergarten teacher Maggie Moeller looks for any clues to tell twins apart. "You look for freckles or any small difference," she said. But often that's not enough in a fast-moving class full of 5 year olds.   "In my class I have one set of fraternal twins, two boys; and last year I had triplets-two boys and a girl," she said.

She has learned to watch their personalities and to try to quickly get to know the multiples.

Deanna Muilenberg and her twin brother Kevin are high school freshmen at Hanson.  "My twin, we're like best friends, " said Deanna. "I love being in school with him.  Twins do have a different relationship, and it's fun knowing how we interact, and seeing how other twins interact with each other."

Moeller said the bond between twins and triplets is evident to the teachers as well.  "They definitely have a special relationship and bond, whether it's sticking up for each other or the brother and sister arguing, you can see it."

That closeness in class can also cause problems. "The biggest challenge is definitely the interruptions," Moeller said. "They tend to correct each other.   You want them to have their own voice, but sometimes you need to remind them it's not their turn."

According to a recent report by the National Center for Health Statistics, the rate of twin births rose 76 percent in the three decades stretching from 1980 and 2009.  Today,  nearly one in every 30 babies born in the United States is a twin.

The research cites the growing use of fertility treatments as one of the key causes for multiple births.

In Alexandria, no one has an explanation for the fact that 23 of the Hanson School's 300 students are either triplets or twins.   But teacher Moeller has a suggestion,  "Name tags would be very helpful."