The round lodged in a cinder block wall, and no one was hurt.
The incident occurred in mid-December at Field High School and involved police from Brimfield Township east of Akron.
Township Police Chief David Oliver told the Akron Beacon Journal on Friday the officers used poor judgment by cleaning their pistols during school hours.
He said they used an isolated, cinderblock room while students were in class.
The officer whose pistol discharged was suspended three days without pay. The other officer received a written reprimand.
The chief, whose department has 134,000 Facebook followers, detailed the incident online.