A first-grade teacher at Cherokee Heights Elementary School in St. Paul was injured Wednesday when an agitated student flung a chair at the teacher, school officials said.

Cherokee Heights Principal Melisa Rivera sent a letter to first-grade families saying, “The student was quickly removed from the classroom. Thankfully, no other students were hurt.”

The teacher, who sought medical treatment, did not return to school Thursday.

Police spokesman Steve Linders said the incident happened about 2:15 p.m. Wednesday and was categorized as an assault. An officer responded but had not filed a report as of Thursday afternoon, Linders said.

Rivera said in her letter that she spent time with the other children from that classroom, answered their questions and reassured them they were safe.

“I’m sorry for the interruption and any anxiety this may have caused your child,” she said.

The principal also said social workers and school staff are always available to talk to students who need help.

Wednesday’s incident was the latest violence between students and teachers in the district since the school year began. There have been assaults — usually by teenagers — at Como Park High School, Creative Arts Academy and other locations.