Is this true?

Jan 7, 6:34 PM (ET)

RENO, Nev. (AP) - Six girls have been arrested after students were invited on Facebook to take part in "Attack a Teacher Day" at two middle schools.

One girl was accused of inviting about 100 students on the social networking website to participate in the event Friday, and the other five were accused of responding with online threats against specific teachers, Carson Middle School Principal Dan Sadler said.

The Nevada Appeal in Carson City reported the girls were booked Wednesday at juvenile hall on a misdemeanor charge of communicating threats. Their names were not released.

While the students insisted it was a joke, Sadler noted they were arrested on the same day a suspended 17-year-old student in Omaha, Neb., fatally shot an assistant principal and wounded his principal before fleeing the campus and taking his own life.

"School shootings really happen. That's why we took it seriously," Sadler told The Associated Press on Friday. "It's not OK, and it's not funny in this day and age if you're going to make a threat against a teacher."

Five of the students attend Sadler's school and the other attends Eagle Valley Middle School. Both schools are in Carson City.

Eighteen students accepted the invitation to participate in the attacks at the two schools, which had been set to take place from 7 a.m. to 9 a.m. Friday. A parent brought the posting to the attention of authorities, Sadler said.

Classes took place Friday without incident at both schools after students were earlier notified of the arrests and parents of the students who were arrested or accepted the invitations were contacted by authorities.

The 12- and 13-year-old students were arrested after allegedly posting threatening statements against six teachers at the two schools. One student used the word "die" before a teacher's name, while others wrote that they would "attack" certain teachers, Sadler said.

No specifics, such as weapons or how the attacks would be carried out, were mentioned, said Carson City sheriff's Deputy Jessica Rivera, the school district's resource officer. The invitation to join the attacks went out either Monday or Tuesday night.

"Even if the six girls meant it as a joke, there's no way to know if the other students who accepted the invitation weren't going to carry out the attacks in some fashion," Rivera said. "The school shooting in Nebraska is just another thing that shows us you can't take this kind of situation lightly."

The girls were released to the custody of their parents after their arrests. They were suspended from school for between three and five days.

The Facebook posting was removed by the parent of the girl who sent out the invitation to join the attacks.

Sadler said the teachers targeted by the threatening comments were shocked by the arrests because the six girls were good students. Some held leadership positions while others had top grades.

"I would say their reaction was 'Are you serious? Is this really happening?'" Sadler said. "The more they thought about it, they said they were not OK with it. This is kind of disheartening to an educator."

Kathy Haas, a Carson Middle School teacher who taught two of the students who were arrested, said she was surprised because they seemed normal.

"It shows you just don't know what's going on in their minds," she said. "I don't understand their motivation. I don't think they think about the consequences because they're young. They're pretty immature then."

The arrests gave teachers at the schools a chance for classroom discussions about online communications with students, Haas added.

"It's a teachable moment and hopefully it prevents it from happening in the future," she said. "Most students know it was wrong. A lot of students said they knew about it (Facebook posting) and deleted it."

Carson City Sheriff Ken Furlong said the case demonstrates the need for parents to monitor their children's online activities.

"They made some pretty violent comments about some teachers, and this isn't even close to a joke," he said. "Children's stresses are so great that they can act out on their frustrations. Parents need to monitor what their kids are doing on communication devices."