In the fall of 2010, Ms. Parks, a third-grade teacher at Venetian Hills Elementary School in southwest Atlanta, agreed to become Witness No. 1 for Mr. Hyde, in what would develop into the most widespread public school cheating scandal in memory.

Ms. Parks admitted to Mr. Hyde that she was one of seven teachers — nicknamed “the chosen” — who sat in a locked windowless room every afternoon during the week of state testing, raising students’ scores by erasing wrong answers and making them right. She then agreed to wear a hidden electronic wire to school, and for weeks she secretly recorded the conversations of her fellow teachers for Mr. Hyde.

In the two and a half years since, the state’s investigation reached from Ms. Parks’s third-grade classroom all the way to the district superintendent at the time, Beverly L. Hall, who was one of 35 Atlanta educators indicted Friday by a Fulton County grand jury.

Dr. Hall, who retired in 2011, was charged with racketeering, theft, influencing witnesses, conspiracy and making false statements. Prosecutors recommended a $7.5 million bond for her; she could face up to 45 years in prison.

During the decade she led the district of 52,000 children, many of them poor and African-American, Atlanta students often outperformed wealthier suburban districts on state tests.

Those test scores brought her fame — in 2009, the American Association of School Administrators named her superintendent of the year and Arne Duncan, the secretary of education, hosted her at the White House.

And fortune — she earned more than $500,000 in performance bonuses while superintendent.

On Friday, prosecutors essentially said it really was too good to be true. Dr. Hall and the 34 teachers, principals and administrators “conspired to either cheat, conceal cheating or retaliate against whistle-blowers in an effort to bolster C.R.C.T. scores for the benefit of financial rewards associated with high test scores,” the indictment said, referring to the state’s Criterion-Referenced Competency Test.

Reached late Friday, Richard Deane, Dr. Hall’s lawyer, said they were digesting the indictment and making arrangements for bond. “We’re pretty busy,” he said.

As she has since the beginning, Mr. Deane said, Dr. Hall has denied the charges and any involvement in cheating or any other wrongdoing and expected to be vindicated. “We note that as far as has been disclosed, despite the thousands of interviews that were reportedly done by the governor’s investigators and others, not a single person reported that Dr. Hall participated in or directed them to cheat on the C.R.C.T.,” he said later in a statement.

In a 2011 interview with The New York Times, Dr. Hall said that people under her had allowed cheating but that she never had. “I can’t accept that there is a culture of cheating,” she said.

Paul L. Howard Jr., the district attorney, said that under Dr. Hall’s leadership, there was “a single-minded purpose, and that is to cheat.”

“She is a full participant in that conspiracy,” he said. “Without her, this conspiracy could not have taken place, particularly in the degree it took place.”

Longstanding Rumors

For years there had been reports of widespread cheating in Atlanta, but Dr. Hall was feared by teachers and principals, and few dared to speak out. “Principals and teachers were frequently told by Beverly Hall and her subordinates that excuses for not meeting targets would not be tolerated,” the indictment said.

Reporters for The Atlanta Journal-Constitution and state education officials repeatedly found strong indications of cheating — extraordinary increases in test scores from one year to the next, along with a high number of erasures on answering sheets from wrong to right.

But they were not able to find anyone who would confess to it.

That is until August 2010, when Gov. Sonny Perdue named two special prosecutors — Michael Bowers, a Republican former attorney general, and Robert E. Wilson, a Democratic former district attorney — along with Mr. Hyde to conduct a criminal investigation.

For weeks that fall, Mr. Hyde had been stonewalled and lied to by teachers at Venetian Hills including Ms. Parks, who at one point, stood in her classroom doorway and blocked him from entering.

But day after day he returned to question people, and eventually his presence weighed so heavily on Ms. Parks that she said she felt a terrible need to confess her sins. “I wanted to repent,” she recalled in an interview. “I wanted to clear my conscience.”

Ms. Parks told Mr. Hyde that the cheating had been going on at least since 2004 and was overseen by the principal, who wore gloves so as not to leave her fingerprints on the answer sheets.

Children who scored 1 on the state test out of a possible 4 became 2s, she said; 2s became 3s.

“The cheating had been going on so long,” Ms. Parks said. “We considered it part of our jobs.”

She said teachers were under constant pressure from principals who feared they would be fired if they did not meet the testing targets set by the superintendent.

Dr. Hall was known to rule by fear. She gave principals three years to meet their testing goals. Few did; in her decade as superintendent, she replaced 90 percent of the principals.

Teachers and principals whose students had high test scores received tenure and thousands of dollars in performance bonuses. Otherwise, as one teacher explained, it was “low score out the door.”

Ms. Parks, a 17-year veteran, said a reason she had kept silent so long was that as a single mother, she could not afford to lose her job.

When asked during an interview if she was surprised that out of Atlanta’s 100 schools, Mr. Hyde turned up at hers first, Ms. Parks said no. “I had a dream about it a few weeks before,” she said. “I saw people walking down the hall with yellow notepads. From time to time, God reveals things to me in dreams.”

“I think God led Mr. Hyde to Venetian Hills,” she said.

Whatever delivered Mr. Hyde (he said he picked the school because he knew the area from patrolling it as a young police officer), 10 months after his arrival, on June 30, 2011, state investigators issued an 800-page report implicating 178 teachers and principals — including 82 who confessed to cheating.

By now, almost all are gone. Like Ms. Parks, they have resigned or were fired or lost their teaching licenses at administrative hearings.

Higher Scores, Less Aid

Some losses are harder to measure, like the impact on the children in schools where cheating was prevalent. At Parks Middle School, which investigators say was the site of the city’s worst cheating, test scores soared right after the arrival of a new principal, Christopher Waller — who was one of the 35 named in Friday’s indictment.

His first year at Parks, 2005, 86 percent of eighth graders scored proficient in math compared with 24 percent the year before; 78 percent passed the state reading test versus 35 percent the previous year.

The falsified test scores were so high that Parks Middle was no longer classified as a school in need of improvement and, as a result, lost $750,000 in state and federal aid, according to investigators. That money could have been used to give struggling children extra academic support. Stacey Johnson, a Parks teacher, told investigators that she had students in her class who had scored proficient on state tests in previous years but were actually reading on the first-grade level. Cheating masked the deficiencies and skewed the diagnosis.

When Erroll Davis Jr. succeeded Dr. Hall in July 2011, one of his first acts as superintendent was to create remedial classes in hopes of helping thousands of these students catch up.

It is not just an Atlanta problem. Cheating has grown at school districts around the country as standardized testing has become a primary means of evaluating teachers, principals and schools. In El Paso, a superintendent went to prison recently after removing low-performing children from classes to improve the district’s test scores. In Ohio, state officials are investigating whether several urban districts intentionally listed low-performing students as having withdrawn even though they were still in school.

But no state has come close to Georgia in appropriating the resources needed to root it out.

And that is because of former Governor Perdue.

“The more we were stonewalled, the more we wanted to know why,” he said in an interview.

In August 2010, after yet another blue-ribbon commission of Atlanta officials found no serious cheating, Mr. Perdue appointed the two special prosecutors and gave them subpoena powers and a budget substantial enough to hire more than 50 state investigators who were overseen by Mr. Hyde.

Mr. Bowers, Mr. Wilson and Mr. Hyde had spent most of their careers putting criminals in prison, and almost as important, they could write. They produced an investigative report with a narrative that read more like a crime thriller than a sleepy legal document and placed Dr. Hall center stage in a drama of mind-boggling dysfunction.

She had praised Mr. Waller of Parks Middle as one of the finest principals in the city, while Mr. Wilson, the special prosecutor, called him “the worst of the worst.”

According to the report, Mr. Waller held “changing parties” where he stood guarding the door as teachers gathered to erase wrong answers and make them right. “I need the numbers,” he would urge the teachers. “Do what you do.”

(When questioned by investigators, Mr. Waller cited his Fifth Amendment protection against self-incrimination.)

Dr. Hall arrived in Atlanta in 1999, the final step in a long upward climb. She had advanced through the ranks of the New York City schools, from teacher to principal to deputy superintendent, and then in 1995, became the superintendent in Newark.

In Atlanta, she built a reputation as a person who got results, understood the needs of poor children and had a strong relationship with the business elite.

Her focus on test scores made her a favorite of the national education reform movement, nearly as prominent as the schools chancellors Joel I. Klein of New York City and Michelle Rhee of Washington. Like them, she was a fearsome presence who would accept no excuses when it came to educating poor children. She held yearly rallies at the Georgia Dome, rewarding principals and teachers from schools with high test scores by seating them up front, close to her, while low scorers were shunted aside to the bleachers.

But she was also known as someone who held herself aloof from parents, teachers and principals. The district spent $100,000 a year for a security detail to drive her around the city. At public meetings, questions had to be submitted beforehand for screening.

In contrast, her successor, Mr. Davis, drives himself and his home phone number is listed.

As long ago as 2001, Journal-Constitution reporters were writing articles questioning test scores under Dr. Hall, but when they requested interviews they were rebuffed. Heather Vogell, an investigative reporter, said officials took months responding to her public information requests — if they did at all. “I’d call, leave a message, call again, no one would pick up,” she said.

Community Pressure

What made Dr. Hall just about untouchable was her strong ties to local business leaders. Atlanta prides itself in being a progressive Southern city when it comes to education, entrepreneurship and race — and Dr. Hall’s rising test scores were good news on all those fronts. She is an African-American woman who had turned around a mainly poor African-American school district, which would make Atlanta an even more desirable destination for businesses.

And so when Mr. Perdue challenged the test results that underpinned everything — even though he was a conservative Republican businessman — he met strong resistance from the Metro Atlanta Chamber of Commerce.

“There was extensive subtle pressure,” Mr. Perdue said. “They’d say, ‘Do you really think there is anything there? We have to make sure we don’t hurt the city.’ Good friends broke with me over this.”

“I was dumbfounded that the business community would not want the truth,” he said. “These would be the next generation of employees, and companies would be looking at them and wondering why they had graduated and could not do simple skills. Business was insisting on accountability, but they didn’t want real accountability.”

Once the special prosecutors’ report was made public, it did not matter what the business community wanted; the findings were so sensational, there was no turning back.

Ms. Parks of Venetian Hills was one of many who wore a concealed wire for Mr. Hyde.

As he listened to the hours of secretly recorded conversations of cheating teachers and principals, he was surprised. “I heard them in unguarded moments,” Mr. Hyde said. “You listen, they’re good people. Their tone was of men and women who cared about kids.”

“Every time I play those tapes, I get furious about the way Beverly Hall treated these people,” he said.

Another important source for him at Venetian Hills was Milagros Moner, the testing coordinator. “A really fine person,” Mr. Hyde said. “Another single mom under terrible pressure.”

Ms. Moner told Mr. Hyde that she carried the tests in a tote bag to the principal, Clarietta Davis, who put on gloves before touching them.

After school, on Oct. 18, 2010, the two women sat in the principal’s car in the parking lot of a McDonald’s. Inside Ms. Moner’s purse was a tape recorder Mr. Hyde had given her. Thirty yards away, he sat in his pickup truck videotaping as they talked about how the investigation and media coverage had taken over their lives.

Ms. Moner: I can’t eat, I can’t sleep, my kids want to talk to me, I ignore them. ... I don’t have the mental energy. ...

Ms. Davis: You wouldn’t believe how people just look at you. People you know.

Ms. Moner: You feel isolated.

Ms. Davis: There’s no one to talk to. ... See how red my eyes are? And I’m not a drinking woman.

Ms. Moner: It has taken over my life. I don’t even want to go to work. I pray day and night, I pray at work.

Ms. Davis: You just have to pray for everybody.

Later, when investigators tried to question Ms. Davis about her reasons for wearing the gloves, she invoked the Fifth Amendment. On Friday, she was one of the 35 indicted.