A New Jersey middle school principal has upset parents for saying girls could not wear strapless dresses to an eighth grade dance because, she said, they'd distract the boys.

"She said strapless dresses … are age inappropriate," Charlotte Nijenhuis, 50, from Whitehouse Station, N.J., told ABCNews.com about her conversation with Readington Middle School's principal, Sharon Moffat.

Readington Middle School in New Jersey has banned girls from wearing strapless dresses, such as these pictured here, to their eighth grade dance. (Getty Images)

Moffat sent out a letter this month, restricting girls from wearing dresses without straps to their eighth grade formal.

"Young gentleman are encouraged to wear collared shirts and trousers," Moffat said in the letter. "Young ladies should wear a skirt, dress with straps or a dressy pants outfit."

Nijenhuis, whose daughter is an eighth grader at the school, said she challenged Moffat's strapless-dress ban. When the principal told her the dresses would distract male students, Moffat said, "Distracting [them] from what? It's a sexist comment."

Several attempts by ABCNews.com to reach Moffat for comment were not successful.

Nijenhuis said she later tried to voice her objections to the Readington Township School District's superintendent, Barbara Sargent, who, she said, supported Moffat's decision.

"The Readington Township School District has a policy regarding dress code, which is being universally applied to the school day and school events," the school district said in a statement. "We regret that a small number of families are upset by this, and we welcome their input and communication."

Other parents are said they were upset about the strapless-dress ban.

"It's more of a personal opinion rather than what's in the best interest of these kids," Melissa May, 37, of Flemington, N.J., told ABCNews.com.

"It's categorizing all these children unfairly," she said. "She's saying the boys don't know how to handle themselves. This whole issue is sending the kids a bad message: What you wear dictates who you are."

May said she would never allow her daughter to go out of the house if she thought she was wearing something "inappropriate."

"We need to put the power in the hands of the parents in what we find appropriate and what we don't find appropriate for them to wear," she said.

While both May and Nijenhuis said their daughters and other students were opposed to the new restriction, it is the parents who were leading the challenge.

Nijenhuis has started a petition for those who oppose the dress policy, and she and other parents and students would attend a meeting Tuesday night to voice their concerns before the school board.

"My hope is that the board agrees and says that they will stand by the prior interpretations that these dresses are well within 21 st century customs," Nijenhuis said.

For now, the strapless restrictions remain in place, with students saying having difficulty finding dresses that adhere to the policy for the June 14 dance.

"I'm hoping they soften it," May said. "Let's not put ideas in their head.

"They grow up so fast anyway."