The report released Tuesday said 80 teachers and principals admitted cheating, The Atlanta Journal-Constitution reported.
Investigators said test scores were manipulated in 44 of the 56 schools they examined, and 178 employees, including 38 principals, were involved.
One teacher said she feared the consequences of not participating.
"APS is run like the mob," she said.
Atlanta's apparent improvement on state tests made the school system a national model. Beverly Hall, the former superintendent, was named Superintendent of the Year in 2009.
Hall in a statement released by a lawyer said she knew nothing of any wrongdoing.
Gov. Nathan Deal, who released the report, said there will be "consequences" for those who cheated. Those could include criminal charges.
The investigation was the largest ever of its kind in the United States.