Nina Lillehei has her first formal gown, navy blue and full-length with a shirred bodice. Her date, Max Horn, has bought his tux.

But the duo is all dressed up with no place to go, now that Southwest High School this year has ruled that Lillehei is too young to attend the Minneapolis school's prom Saturday night.

Students say the school's decision this year to enforce its no-sophomore policy has left as many as 17 couples banished from the "Paint the Night Away" prom at Walker Art Center. Those students and their parents are crying foul because the school let some sophomores into the prom last year.

Not this time. Just like the bans on tobacco, booze and "grinding" on the dance floor, the prohibition on younger dates is designed to keep the prom under control. Students say district and school officials have told them that the school is simply enforcing a rule that's designed to keep the event special for older students, and to shield younger students from some of the social pressures of prom night.

"Juniors and seniors want to have a special day, and we support them," said Bill Smith, the Southwest principal.

Horn, a junior at Southwest, asked Nina to prom by spelling the word out in tea lights on the sidewalk of her Lowry Hill home. Then he turned in the form listing his date, and got the bad news.

"We found out last Friday," said Searcy Lillehei, mother of Nina, a Blake sophomore. "She called me in tears."

Some students got the news after they'd invested in dresses that can run to several hundred dollars and typically can't be returned. "They could wear it next year, but it may not fit," said Linnea Sorlien, a sophomore who found out two weeks ago she's ineligible.

Gary Amoroso, who heads the Minnesota Association of School Administrators, said districts tend to set their own rules about age limits on proms. The policy varies even within Minneapolis.

But what irritates some Southwest students is that they know of several sophomores who attended last year. They assumed that meant that the school wasn't serious about its rule.

"There was like a small handful," said Gabe Epstein, who attended as a sophomore with a junior friend. Although chaperones checked his school ID, which show a student's year in school, no one blinked, he said. "It sucks and it's stupid," Epstein said about the rule.

The principal of Southwest, a school that has been cited nationally for its rigorous academics, said the rule has been in place for at least five years. Smith said that a strict definition is easier than trying to make judgments about whether two students have been going together long enough to merit an exception. He concedes that there may have been mistakes in admitting younger students in the past.

Smith added that students in the school's two younger grades had their Morp (that's prom backwards) event on May 5 with a luau theme.

But that's left some unsatisfied.

"I've never worn a long dress before," Nina Lillehei said, her voice trembling a bit. "It was exciting." She'd tried on maybe five dresses at three stores before settling on a BCBG-label dress that cost around $200. "I just thought the dress was really beautiful and I was excited that it fit."

Luckily for her mother, the dress was purchased at Macy's, which has a more liberal return policy than some stores, which don't allow prom dresses to be returned, for fear they'll be worn for the dance and then brought back.

The Horns decided to buy a $400 tux rather than rent one because they figured Max was looking at two proms during high school, plus another planned formal event this fall.

Associate Superintendent Theresa Battle denied the Horn family's formal request for a waiver from the policy.

"I am unwilling to make an exception for rules that are included in the student handbook," Battle told him in an e-mail.

"It's such a shame that over 30 students will finish the school year with so much disappointment and anger about this," said Max's father, Ben Horn.

Smith said he thought all students knew of the junior and senior rule. "It was a tad surprising. Communication is always a problem," he said. "I'm sorry if some people were inconvenienced or made plans that didn't seem consistent with what was going on, but I don't know how to deal with that."

But some parents aren't satisfied. "I just think it's very unreasonable," said Ginny Templeton, Linnea's mother. "It's really their first significant relationship and then they're excluded. It's just one of those unfairness-in-life things where it doesn't make any sense."

Some students will still venture to Lake Harriet for their prom photos, and some plan to go to dinner even if they won't get inside the prom. As for Searcy Lillehei, she hasn't returned Nina's dress, which still bears its store tags.

"We're kind of holding out for a last-minute reprieve," she said.

Steve Brandt • 612-673-4438