Authorities said a stove was left on overnight inside Foundations Academy, at 2823 Sanderford Road. Teachers smelled the gas, turned off the stove, opened windows and called 911.
"It quickly went from something that could have been serious to something that was not," said John Fanning, battalion chief for Raleigh Fire Department.
About 60 children and eight staff members left the building and sat calmly outside, but none showed any symptoms of carbon monoxide poisoning, Fanning said.
"Our teachers did a wonderful job remaining calm and keeping the children entertained with outside activities," Foundations Academy Director Dan'elle Allen said in a statement. "All the parents were notified and everyone is doing fine. There was no evidence of carbon monoxide."
Pat Hinton, whose daughter attends Foundations Academy, said parents were being asked to wait for wellness checks to be complete before taking their children home.
Students and teachers were back inside the building by noon.