Police said the victim was a 13-year-old boy from Downingtown, but they did not say whether he was injured.
They indicated that two 13-year-old girls and a 13-year-old boy were the alleged attackers. The boy and one of the girls are from West Chester; the other girl lives in Downingtown.
Patricia C. McGlone, director of public information and development for the Downingtown Area School District, said in a statement Friday the video showed students fighting on a bus, with one of them wearing a Downingtown Middle School sweatshirt.
After watching the videotape, Indeglio was able to identify the pupils. Their parents were alerted, and the matter was turned over to the state police for investigation, McGlone said.
The fight happened while the bus was traveling on Shadyside Road near Marshallton Thorndale Road, the report said.
The district moved quickly to term the incident bullying.
"The students involved in this incident were disciplined expeditiously according to district policies," Superintendent Lawrence Mussoline said. "The Downingtown Area School District does not tolerate inappropriate behavior in school or on our school buses."
Neither McGlone nor Indeglio could be reached Friday to determine the exact disciplinary measures taken. Authorities did not release the identities of the three minors.
McGlone said the middle school sent home a letter to parents Friday. The letter described the bullying and steps administrators had taken.
"In a school of over 1,300 students, there are a very small percentage of reported bullying incidents," the letter said. "However, we take the issue very seriously."
The letter said school officials were "acutely aware of the issue, and it is becoming more and more of a focus for our teams and entire building. It's not enough to simply report bullying; our culture needs to reflect the stance that none of us are accepting of bullying behavior."
The Jan. 20 incident in West Bradford Township followed by just nine days a videotaped bullying attack in Upper Darby in which six teens kicked and beat 13-year-old Nadin Khoury. A seventh teen recorded the attack; the tape was widely viewed on TV and the Internet.
Five of the boys admitted Feb. 10 to charges of false imprisonment, reckless endangerment, simple assault, and conspiracy. They were sentenced to 60 to 90 days of curfew, 45 days of electronic home monitoring, and 16 hours of community service.
The sixth boy, a 16-year-old, was charged with the felony offenses of kidnapping and aggravated assault. He admitted to lesser misdemeanor charges of false imprisonment, reckless endangerment, and simple assault.
He was in custody at the Juvenile Detention Center in Lima pending a March 3 hearing.
Contact staff writer Bonnie L. Cook at 610-313-8232 or firstname.lastname@example.org.