No one was reported injured in the incident involving an "active gunman" in the Ronald E. McNair Discovery Learning Academy in DeKalb County, Georgia near Atlanta.
"There have been reports of shots fired. There are no injuries," Melvin Johnson, the DeKalb County school board chairman, told WSB TV Atlanta.
Teachers helped evacuate the school while police moved inside the building and apprehend the suspected gunman, who was not immediately identified.
As the shooting unfolded, US President Barack Obama was coincidentally tweeting about the need to strengthen US gun laws.