Their dresses have been bought and their boyfriends have rented tuxes, but Principal Timothy Woodward won't consider their special request.
"The age we set is to best protect the integrity of a high school event," he told ABC's affiliate, citing concerns about alcohol being smuggled in to the dance.
But the girls insist that the school handbook allows for an exception -- "No one over 20 years old will be admitted to any dance unless pre-approved by the administration" -- and they have filed forms that they say the principal is ignoring.
The guess permission form states, "Special permission from the principal must be requested for any guest who exceeds high school age, 20."
School officials say that if the girls were married, they could bring their husbands.
"Does he want us to go out and get married? Teen marriage? Is that what they're trying to do," asked Lucas, a good student who wants to be an anesthesiologist.
She cannot understand why the school would not welcome her boyfriend – a Navy reservist who wants to be a military policeman – who was approved and attended her Homecoming dance.
"He is trying to get into law enforcement, so he's not going to do something to jeopardize my graduation or his own future," she told ABCNews.com.
Her stepfather is astounded the school would reject his daughter's boyfriend, Jordan O'Roark. "He's a really good boy," said Michael Payton, who argued with both the principal and the school board.
Adrenna Lucas, 24, said her sister Megan's boyfriend Josh Mullens, a 21-year-old plumber, had played football for Spotswood and had even chaperoned some school events.
"He comes over and helps my parents mow the yard and when my Dad had back surgery, he came out and mulched and flowered for my Mum," she told ABCNews.com. "He's a good guy."
The girls were told they could attend alone, but Offenbacker says, "I'm not the type of person who just goes to a dance with girls, especially when I dated this boy for over a year. I wouldn't feel right."
The girls' parents offered to chaperone the May 16 prom, but the school declined.
"I'm more upset than she is," said Offenbacker's mother, Wendy Payton. "This is ridiculous and so sad that this is her last dance as a high school student."
"We teach her to be who she wants to be and what you put into something is what you get out of it. When she is wrong, we hold her accountable, and when she does right, we support her," Payton told ABCNews.com. "She is not asking for policy to be broken or to bend the rules."
The Paytons are also looking for an apology and if the principal does not budge, they plan to have a private prom party at a nearby skating rink.
"She was a cheerleader and supporter of Spotswood 100 percent," said her mother. "We are devasted. I am not stopping until the very end. She has earned this."
So too, has Tyler Frost, 17, of Findlay, Ohio, who in his senior year has never attended a prom. He is being threatened with suspension if he attends a prom with his public school girlfriend, but he refuses to be shut out.
Frost, 17, attends Heritage Christian High School, where dancing, listening to rock music and holding hands and kissing is outlawed.