ATLANTA — A county school system in metropolitan Atlanta on Thursday became the nation's first in nearly 40 years to lose its accreditation, and the governor removed four of its school board members for ethics violations.

The school system in Clayton County, just south of the Atlanta city limits, was ruled unfit for accreditation by the Southern Association of Colleges and Schools, one of the nation's six major private accrediting agencies, after school board members failed to meet the group's standards for leading a school system.

An investigation by the agency found that county officials had not made sufficient progress toward establishing an effective school board, removing the influence of outside individuals on board decisions, enforcing an ethics policy or meeting other requirements for accreditation, Mark A. Elgart, the chief executive of the association, announced Thursday at a news conference.

County officials said they were planning to appeal the decision.

The loss of accreditation could impair the ability of Clayton County students to attend some colleges and earn scholarships. It could also prevent teachers from receiving benefits if they change school systems and could mean a loss of money for pre-kindergarten education.

Two hours after the accreditation agency's announcement, Gov. Sonny Perdue of Georgia removed four Clayton school board members, Michelle Strong, Louise Baines-Hunter, Yolanda Everett and Sandra Scott, for violations of the state's open meetings act and ethics code.

"The fate of the Clayton County school system is now in the hands of the voters," Perdue said in a statement. "Through the elections to replace these four board members, they can send a clear signal that the kind of behavior that has led to this ruling and the system's loss of accreditation will not be tolerated."

The accreditation loss and the removal of the board members generated anger and concern about the fate of the 52,000 students in the largely black district's 59 schools.

School accreditation is voluntary, but more than 90 percent of Georgia school systems are accredited, according to the agency. Many colleges require or prefer diplomas from accredited high schools, and until Georgia legislators changed the law this spring, one of the state's largest college scholarship programs required students to graduate from accredited schools.