Atlanta police said the wounded student, who was shot in the back of the head, was taken "alert, conscious and breathing" to an area hospital. The shooting occurred outside of Price Middle School, just south of downtown.
Atlanta Public Schools said on its website that the suspect also was a student at Price. The circumstances surrounding the shooting remain unclear. The suspect was taken into custody.
All other students are said to be safe. However, a teacher reportedly suffered minor cuts and bruises.
Students were being kept at the locked-down school some two hours after the shooting but television footage showed some of them being dismissed.
The Associated Press contributed to this report.