LOS ANGELES (Reuters) - Angry parents demanded the resignation of a California high school vice principal after she lifted the skirts of teenage girls at a dance to make sure they were wearing "appropriate" underwear.

Parents at Rancho Bernardo High School in suburban San Diego say the vice principal, Rita Wilson, made the girls prove that they were not wearing skimpy thong panties before they were allowed into the dance on Friday.

In some cases, said Rancho Bernardo parent Kim Teal, girls also were made to partially undress if Wilson or another teacher suspected that they weren't wearing bras.

"These girls feel violated," said Teal, whose daughter Rebecca, a sophomore, was asked about her panties but escaped a search after telling Wilson that she was not wearing a thong.

"One girl just cried after having to tell her father this story, she was hiding her head in a sweatshirt," Teal said, adding that the girls had their skirts lifted in front of men and their male classmates.

"After a while the girls finally got the idea that they shouldn't say 'thong' when they were asked, even though that's all they wear now. They won't be caught dead in the locker room wearing regular underwear," she said Tuesday.

Wilson and Paul Gentle, Rancho Bernardo's principal, were unavailable for comment on the skirt-lifting.

Don Phillips, superintendent of the Poway Unified School District, said students, staff and others were being interviewed to determine what happened at the dance, which he said was attended by about 725 pupils.

"The principal is talking with the parents involved," he said. "We are taking this seriously and want to ensure that any actions to be taken are based on the facts of the situation."

Teal, a 43-year-old attorney, said she learned about the skirt-lifting from her daughter, whose friends were forced to show their panties in front of boys, teachers and police officers standing at the door.

She said most of the girls who wore skirts or dresses to the dance, which had a "blast from the past" theme, reported being grilled about their underwear or forced to show them to Wilson or another teacher.

Teachers also checked several boys who were wearing togas, Teal said, and some girls were asked about their bras.

"I just got a call from one mom who said her daughter was wearing a poodle skirt and an off-the-shoulder top and a teacher reached right out and grabbed the front of it and pulled it down to check," Teal said.

Teal said she and other parents would demand the resignation of Wilson and any other teachers involved and would also consider filing a lawsuit against the school district for violating the civil rights of their daughters.