An 11-year-old from New Holland Elementary School has been harassed and bullied by a sixth-grade "girl gang'' for weeks, her mother says.

A 16-year-old from Columbia High School was beaten up by a group of girls after school in April and ended up transferring to a private school.

Meet a formidable challenge for Lancaster County school officials: the girl bully.

She's in elementary, middle and high schools here.

She differs from boy bullies in some significant ways.

She intimidates by gossip, rumors, cruel comments or exclusion.

She can continue the harassment for years, drawing sidekicks into her circle.

Sometimes, but not often, she physically lashes out at her victim, punching, tripping or throwing things at her.

She's become such a phenomenon here and across the country that she's the topic of a teen movie titled, appropriately, "Mean Girls.'' "I think girls are getting tougher and I'm not sure why,'' says Kris Dimon, the mother of the 11-year-old from New Holland, who also says she doesn't know "if it's a survival mechanism or what.''

Schools have responded by setting up anti-bullying programs that foster respect and compassion among students.

It's not always an easy task.

The problems with girl bullies at local schools were spotlighted this April, when 16-year-old Rebecca Diffenderfer had her nose broken when a group of girls attacked her after school.

The girls were later expelled but parents said they were concerned about what they described as escalating violence among students at the school. The district responded by appointing a task force to address the problem.

Other reports of problems began to surface.

Shayna Watson, 24, is the older sister of the 12-year-old sixth-grader at Hand Middle School.

She says her sister's broken ankle was the culmination of months of harassment.

"There was name-calling, cursing, throwing stuff, brushing up against her in the hallway,'' she says.

Watson's family tried to address the problem by meeting with school officials, and even asking their minister to intervene. Nothing has worked, she says.

"There's always been bullies,'' she says. "Now it's more physical. Now they're starting to use weapons, as opposed to pushing and spitballs. They want to take it to the next level. They want to hurt each other bad, and that's kind of scary.''

In New Holland, Dimon called for a formal anti-bullying program. New Holland Elementary does have a program to deal with conflict and anger but will examine a more formal program this summer, says Principal Steve Rockelman, who oversees fourth to sixth grades.

Everyone -- teachers, students, bus drivers, cafeteria workers -- needs to be united to stop bullies, Dimon says.

"Enough,'' she says, "is enough.''

John Sparmblack is the 12th-grade principal at Hempfield High School. Like other principals here, he followed the media coverage of the case involving the Columbia student this spring.

"I felt bad for Columbia,'' he says, "but it's not just at Columbia. It's at every school.'' Girl bullying, Sparmblack and other school officials here say, is not a new problem for schools, nor is it necessarily getting worse.

Schools, and now the public, are just more aware of it these days, and how girl bullies differ from boy bullies.

"With girls, it's uglier and more long-term,'' he says. "It's very psychological, as opposed to physical. The effects last longer and are much more hurtful.'' Boys tend to duke it out, and then put the conflict behind them. Not girls, Sparmblack says, adding, "Physical bullying is easier to get over than psychological bullying.''

Bullying, for both girls and boys, starts at an early age. Three years ago, Hempfield officials took a survey of kindergartners to third-graders at Landisville Primary Center.

A total of 71 percent said they had been hit, kicked, punched or teased by another student at school, said Principal Lyn Schmid.

That number dropped to 49 percent -- still almost half of students -- after the school started to focus on teaching social skills to deal with bullying.

Susan Sneath, a guidance counselor at Schaeffer Elementary School in Manheim Township, says girl bullying starts as early as kindergarten or first grade, when a girl will exclude another from a birthday party or sleepover.

This year, Sneath had to deal with girls teasing each other about being "fat'' after a tumbling exercise in gym class.

"When you think of bullying, you think of a big kid on the playground taking a younger kid's money, and your eye goes to boys,'' she says. "I see more emotional bullying with girls.''

Girls can get physical, butting in line, pulling backpacks or chasing each other, but they often can exhibit that behavior against boys as well as girls, Sneath says.

By middle school, girl bullying can take a more insidious form, as students start getting on the computer.

"I have a really hard time with instant messaging and e-mailing,'' says Kim Moore, guidance counselor at Marticville and Manor middle schools in the Penn Manor School District. "Someone makes an innocent comment, or what they believe to be innocent. ... The rumors can get pretty malicious.''

Schools have a variety of approaches to stop bullying, including better supervision of playgrounds and even making bullies call their parents to report their own behavior.

At the middle school level, Moore says girls take part in "mediations,'' where they are shown how to deal with each other, how to choose their words carefully for example, and not make assumptions about what someone else is saying.

Sparmblack says girl bullying seems to peak between fifth and ninth grade. Schools need to be aware of the problem, and take action when they see it, he says.

"In high school, ninth is the worst for that kind of behavior, picking on each other, isolating another girl with rumors,'' he says.

One girl at Hempfield was so upset by bullying last year that she ended up transferring to another school, even though school officials tried to address the problem.

It still bothers Sparmblack.

"Out of 2,400 kids that's not bad, but it's one too many,'' he says.