Atlanta Fire Cpt Marian McDaniel also says a teacher suffered minor cuts and bruises but was treated on the scene at Price Middle School.
Earlier, a police spokesman said he was headed to the school about 2 miles south of downtown following reports of a shooting.
TV news helicopters show a swarm of Atlanta police officers at the school.
McDaniel said the shooting victim was taken to Grady Hospital but information on the teen's condition was not immediately available.
The shooting is the latest to occur as the United States wrestles with a spate of gun violence, most recently a massacre that left 20 young children and six adults dead at the Sandy Hook elementary school in Connecticut last month.
In the wake of that shooting President Barack Obama vowed to introduce gun reform.