The sound of crinkling paper fills the classroom at the Spring-Ford 5/6 Grade Center in Royersford. Each of the 50 girls has crimped a corner of the pink paper heart she holds - an exercise on the impact of middle-school zingers.

"You're not good enough to hang out with us." Crunch. "Did your mom dress you today?" Crush. "You're a jerk."

By now, everyone's heart is a battered, knotted wad of hurts. "That's what I think happens when we hear hurtful things," says Mari O'Drain, a Spring-Ford counselor and one of the leaders of Club Ophelia, a weekly gathering of 'tween girls and high school-age mentors. "It crumples our hearts."

More than ever, schools, community groups and individual families are throwing girls life preservers - usually in the form of summer camps and after-school clubs like the one in Spring-Ford - to help them navigate the often treacherous waters of middle school.

"Childhood is evaporating," said social worker Paula Singer. She codirects Movin' Up, a weeklong camp in Bryn Mawr that aims to "inoculate" girls against the "culture of middle school."

In many ways, it's the same painfully familiar place - that province of geeks and dorks and queen bees, of who sits next to whom at lunch, of worries over being too thin or too fat, of wearing all the wrong labels, of hallway whispers, of best friends one day, I'm not your friend anymore the next.

But for this generation, experts say, the experience has intensified with the rise of cyber-bullying and sexualized images of girlhood. It even has a clinical name: relational aggression.

Adolescent females, particularly 10-to-13-year-olds, use a nasty type of sniping - showcased in the movie Mean Girls and as old as the Cinderella fairy tale - to attack one another, researchers say. About 40 percent of preteens listed being teased as their top safety concern in a 2003 Girl Scout Research Institute survey.

"It isn't just girls being girls," explained Cheryl Dellasega, author of Surviving Ophelia and a professor of humanities and women's studies at Pennsylvania State University. "It's the use of behaviors and words to hurt another girl. Instead of kicking or punching her, you start a rumor, you make fun of her, you tell her you won't be her friend unless she does what you want her to."

As girls near puberty, the risk of eating disorders, depression and self-inflicted cutting increases, in part because some struggle with media-built expectations and loss of identity, experts say. Researchers often cite relational aggression as a contributing factor.

Dellasega, who developed the Club Ophelia model, has trained about 300 instructors as mean-girl behavior has become more prevalent in schools, she said. "Principals tell me it's all this relational-type stuff," she said. Girls are getting into "word wars."

Club Ophelia, Movin' Up, and other initiatives aim to show preteens how relational aggression hurts others, then educate them on alternatives. Body image, assertiveness, and good eating habits are part of the mix.

"Our programs want to take girls who are healthy and keep them healthy," said Deborah Meyer, executive director of Moving Traditions, a Jenkintown nonprofit. In 2002, it launched Rosh Hodesh: It's a Girl Thing!, which takes its name from a monthly Jewish holiday dedicated to women. An initial 40 groups across the country have expanded to 240 in 29 states and Canada, Meyer said.