The amendment would allow a new state body to select private operators to run taxpayer financed schools. Backed by Gov. Nathan Deal, the measure is on the Nov. 6 ballot.
The opposition coalition announced Tuesday includes associations of teachers, parents, superintendents and local school board members, along with the Southern Christian Leadership Conference, the NAACP and other civil rights organizations.
Opponents argue the amendment is unnecessary, saying local education boards and the state board of education can already issue charters. They say the plan would steer taxpayer money to corporations that run schools for profit.
Proponents say a new path for charter schools would give parents more choices.