For 10 years, Christy McCanna had organized and chaperoned the homecoming dance at Lampeter-Strasburg High School.
But after witnessing what went on at last year's dance, McCanna quit.
Girls were bent over, their backsides thrust in the air, rubbing against the torsos of boys, groups of boys and other girls.
Students formed circles around the dancers so chaperones couldn't see what was happening.
The dancing "was over-the-top offensive," the L-S social studies teacher said.
So offensive, in fact, that L-S canceled this year's dance and held a talent show instead.
The school is believed to be the first public high school in Lancaster County to take such drastic action in response to "dirty dancing."
But officials at other county schools said they, too, have had to crack down in recent years on sexually explicit dancing, commonly known as "grinding" or "freaking," at school-sponsored events.
Some schools have imposed rules that allow only face-to-face dancing, booting students who don't comply.
Chaperones at other schools patrol the dance floor with flashlights so they can identify students who are dancing inappropriately.
Other schools flick on the lights and cut the music when dancing gets out of hand.
The need to more closely monitor students at what is supposed to be a carefree, fun event has made it more difficult to recruit adult dance chaperones, officials said.
Because of the potential for problems, some county schools have shortened the length of dances or reduced the number they sponsor each year.
The reactions are part of a nationwide backlash against "dirty dancing" by students.
Schools in other parts of Pennsylvania, New Jersey, Florida, Ohio, New Hampshire, Nebraska and Missouri have recently banned explicit dancing or canceled dances altogether because of lewd dancing, according to news reports.
Penncrest High School in Media last year went so far as to specifically ban "front-to-back touching," "grinding of genital areas to buttocks" and the straddling of legs or hips at school dances.
Crackdowns here have been less specific, with most schools attempting to enforce existing policies that generally ban "inappropriate" dancing or "suggestive moves."
Dances started to get more raunchy about four or five years ago, county school officials said.
Some attribute the change to the growth in popularity of hip-hop and rap music, which spawned a more physical style of dance that has filtered down from dance clubs and music videos to high school cafeterias and gyms.
"Kids can go to Rick's Place and other clubs and dance like that, but what they don't get is that what is appropriate in places like that isn't appropriate here," said L-S principal Carrol Staub.
Staub said his school tried for three straight years to get students to clean up their acts on the dance floor.
L-S stressed to students it would enforce the school district's policy on appropriate dancing in announcements and on printed notices on dance tickets.
It also began removing students whose dancing crossed the line and turning on the lights "full blast" if large numbers of students didn't comply, Staub said.
"None of these completely eradicated the grinding," he said.
"There would be lines of students doing the bump and grind, with girls bending over for boys and other girls," he said. "Apparently, this was to excite the boys.
"The kids would dance in very tight-knit beehive groups so you could never get to the center of it."
When asked by chaperones to stop grinding, students generally would comply, Staub said.
"But you'd turn around, and 10 minutes later, they'd be doing it again," he said. "The bulk of the kids were doing it."
The lewd dancing prompted complaints from students, parents and chaperones, he said, and made it much harder to recruit volunteer chaperones.
"Nobody on the staff wants to do it because it's a horrible night just running around yelling at kids all the time," Staub said.
The L-S school administration felt it had no choice but to cancel this year's homecoming dance, he said.
"It's kind of disappointing, and I do feel bad for the kids," McCanna said.
"But at the same time, we're a school, and I really don't think we should be supporting that kind of behavior.
"You ask the kids why they do it and they say, 'That's just how we dance.' "
Warwick High School last year notified students that only "face-to-face" dancing would be permitted at school events.
Attached to every ticket are rules on appropriate dancing.
Manheim Township High School principal Debby Mitchell went on the school's television station last year to warn students about "grinding" and other inappropriate dance styles at the upcoming prom.
At McCaskey High School, chaperones circulate through the dance floor with flashlights and warn students if their dancing is inappropriate.
Those who don't comply with warnings are sent home.
Like many other schools in the county, McCaskey also does "attire checks" at the door to make sure students comply with dress codes.
At Donegal Middle School, students who dance inappropriately are sent to a "time-out" area in the lobby of the middle school gym, principal Judy Haugh said.
The school a few years ago also shortened its dances from three hours to two, which has reduced problems.
"It is much better with the earlier time frame, and we get more volunteers" to chaperone, Haugh said in an e-mail.
"Two hours seems to be long enough for them to enjoy being together and has reduced our 'relationship' break-up rate."
Ephrata High School used to host three dances a year but now holds only two - homecoming and prom, district spokeswoman Stephanie Gingrich said.
Other schools are de-emphasizing the dancing aspect of social events.
Conestoga Valley and Manheim Central middle schools, for instance, host dances that include other activities, such as games, food and prizes.
But officials at other schools say their dances remain as popular as ever, despite the challenges posed by "dirty dancing."
"Dances are hugely popular. Homecoming is the fall social event," Solanco School District spokesman Keith Kaufman said in an e-mail.
Nancy Herr, principal of Landisville Middle School, said school dances provide an important "gateway to young adulthood" for her school's students.
Jim Dague, principal of Centerville Middle School, agreed.
"There are few opportunities for young adolescents to gather in a safe, drug-free environment and have fun," he said in an e-mail.
"Seeing kids laughing and having a good time is priceless."
Staub said the Lampeter-Strasburg administration has yet to decide whether to bring back the homecoming dance next year.
That decision will depend, in part, on how students behave themselves when they hit the dance floor next May at the school-sponsored prom.