The shooting at the Westbrook Elementary School in Taylorsville, a Salt Lake City suburb, occurred shortly before classes began in the morning, while most students were still outside the building, said Granite School District spokesman Ben Horsley.
No one else was injured but the sixth-grade teacher, who suffered a single bullet wound to her leg and was taken to a nearby hospital in fair but stable condition, Horsley said. She was later listed in good condition and alert, with family members at her side, the spokesman said.
Horsley said he had no information on how the teacher had the gun holstered or what caused it to discharge. But a preliminary investigation by school district police found the shooting appeared to be accidental and not the result of negligence, he said.
Utah state law allows private citizens, including teachers, to carry concealed firearms to work with a special permit requiring prior gun-safety training and a background check.
In keeping with the law's privacy provisions, the school had not been aware the teacher was a permit holder, Horsley said.
"The law's specific. We're not allowed to ask, and she's not required to tell us," he said. "The intent of a concealed-carry permit is to have the strategic advantage of people not knowing that you're carrying, so that you can defend yourself."
Teachers who do bring a concealed weapon to work must keep it on their person at all times, and are barred from leaving it in a drawer or cabinet, even if under lock and key, he said.
Horsley said the incident marks the first time since the law's passage about a decade ago that anyone with a concealed-carry permit has had their gun go off by mistake in a school.
"We have parents who are concerned about a teacher bringing a weapon into the school, and we have referred those parents to the legislature, as we only have the ability to comply with the law," he said.
He said hundreds of public school faculty in Utah attended free gun-safety classes for teachers organized by concealed-carry advocates following the December 2012 massacre of 20 school children by a gunman in Newtown, Connecticut.