The case of a teenager in Massachusetts who killed herself after a relentless, months-long bullying campaign shows how the common schoolyard behavior is evolving in dangerous new ways online.

Six students face felony charges in the death of Phoebe Prince, 15, who hanged herself in January after being subjected to verbal assault and threats of physical harm. Some harassment occurred online on Facebook, in text messages and in other high-tech forms, a contemporary development in the age-old practice, experts said.

The bullying of Prince far exceeded the limits of normal teenage relationship-related quarrels, said Elizabeth Scheibel, prosecutor in the South Hadley, Massachusetts, case.

Prince was targeted with such insults as whore after she dated a popular high school football player, who had also dated one of the accused girls. Prince was a newcomer from County Clare, Ireland, and had attended boarding school in Limerick.

The accused girls have come under online attack since Prince's death with fake websites set up under their names linked to media accounts of the case. The sites attracted reams of anonymous comments and threats.

Allegations that school officials knew of the bullying but failed to intervene have sparked outrage.

The actions -- or inactions -- of some adults at the school are troublesome, Scheibel said.

A LOT OF PEOPLE KNEW

But no adults have been charged in the case. Scheibel said their failure to help did not amount to criminal behavior.

The school knew something, said Judith Vessey, a professor at the Connell School of Nursing at Boston College who has done extensive research on bullying. The mother knew something. Friends and bystanders knew something.

A lot of people knew what was happening and could have intervened.

Intervention by bystanders is crucial to stopping the downward spiral in bullying cases, she said.

You would like to think that people would examine their own role and what they could do to make it not happen again, said Scott Seider, professor at Boston University's School of Education.

Three girls were arraigned and pleaded not guilty in Prince's case this week to a variety of civil rights violations and stalking charges. A fourth girl and two boys face similar charges. The boys, both of whom briefly dated Prince, also are charged with statutory rape.

Bullying is pervasive in U.S. schools. A U.S. Department of Education report in 2005 found 14 percent of students aged 12 through 18 said they were bullied in the previous six months.

The typical concept of bullying -- intimidation of a child perceived as weak by another -- is too simple, Vessey said.

Especially in girls, bullying can be about social toxicity, she said, describing eye rolls, the exclusions, the whole 'mean girls' thing.

One of the things that puts kids at risk is the notion of difference, she said. This young woman had those risk factors.

On the day she hanged herself from a stairwell, Prince was verbally harassed in the school library, in the hallways and while walking home from school, prosecutors said.

ATTEMPTING SUICIDE

Bullying may play a bigger role than is commonly understood in teen suicide, experts also said. The annual suicide rate among Americans 15 to 19 years old is about seven per 100,000, according to the Centers for Disease Control and Prevention. Teenage boys are more likely to commit suicide than are girls.

A CDC study also showed 14.5 percent of U.S. high school students reported seriously considering suicide during the year preceding the survey, and 6.9 percent said they had attempted suicide once or more in the same period.

Massachusetts lawmakers in March approved a bill that would ban bullying, including cyber-bullying, but versions of the bill must be reconciled by lawmakers before it can become law.

The legislation came in response to the Prince case and the suicide of an 11-year-old boy in Springfield, Massachusetts, last year. Carl Joseph Walker-Hoover had been subject to relentless anti-gay taunts before killing himself.

Having a statute may do little to stop bullying and could make children more wary of reporting incidents and setting themselves up for retribution, Vessey said.

When you have a zero-tolerance program, kids won't tell on one another, she said.

(Editing by Ellen Wulfhorst and Bill Trott)