Six police units were sent to the school’s ancillary premises on Kungsgatan in central Vimmerby and all pupils involved in the fighting were ordered to remain in their classrooms until police arrived.
One female teacher has been taken to hospital in Västervik to be treated for facial injuries, Sveriges Radio reports.
“There was a fight between some students, in connection with which a chair was thrown that hit the teacher,” police officer Göran Wester told Sveriges Radio.
School principal Agneta Kling said the violence was the culmination of a lengthy feud between rival groups from the school’s remedial classes. She described the mood in the school’s Kungsgatan premises as “scary and hateful”.
“There was a lot of bloodshed up there,” she told Sveriges Radio.