Three students at a Coventry school have been excluded over "cyber bullying".
Wendy Tomes, headteacher at Sidney Stringer Academy, issued a letter telling parents malicious comments were made on the Facebook networking site.
"The students involved have been identified, and in many cases face fixed term exclusions," she said.
Police said they had spoken to a boy who was the subject of comments but were leaving the matter to the school.
Ms Tomes said there were about 18 people involved in the cyber bullying incident, not all of them Sydney Stringer students.
'Appalled at actions'
She added that all of the schools investigations lead them to believe the incident had started "over a girl".
She said the mother of the student involved had "quite rightly" contacted the school after going onto her son's Facebook account and discovering that he was being threatened with being attacked.
"We are appalled by the actions of some of our students," she said.
Three of the students had been excluded and their families had received a visit from the school, she said.
Three more pupils were facing "internal exclusion" - being kept away from other pupils.
Supt Ron Winch, said: "Incidents of bullying, be it online or otherwise, tend to be dealt with initially in-house by schools themselves and that is what has happened in this case.
"It would be impractical for the police to intervene in all cases of bullying.
"Police officers have spoken to the boy who has been subject of the comments, and the boy's parents, and they are happy with this approach."
He added there would be an investigation to see if there had been any criminal behaviour.