ATLANTA >> In one of the biggest cheating scandals of its kind in the U.S., 11 former Atlanta public school educators were convicted Wednesday of racketeering for their role in a scheme to inflate students’ scores on standardized exams.

The defendants, including teachers, a principal and other administrators, were accused of falsifying test results to collect bonuses or keep their jobs in the 50,000-student Atlanta school system. A 12th defendant, a teacher, was acquitted of all charges by the jury.

The racketeering charges carry up to 20 years in prison. Most of the defendants will be sentenced April 8.

“This is a huge story and absolutely the biggest development in American education law since forever,” said University of Georgia law professor Ron Carlson. “It has to send a message to educators here and broadly across the nation. Playing with student test scores is very, very dangerous business.”

A state investigation found that as far back as 2005, educators fed answers to students or erased and changed answers on tests after they were turned in. Evidence of cheating was found in 44 schools with nearly 180 educators involved, and teachers who tried to report it were subject to retaliation.

Thirty-five educators in all were indicted in 2013 on charges including racketeering, making false statements and theft. Many pleaded guilty, and some testified at the trial. Atlanta School Superintendent Beverly Hall never went to trial, arguing she was too sick. She died a month ago of breast cancer.

Hall insisted she was innocent. But educators said she was among higher-ups pressuring them to inflate students’ scores to show gains in achievement and meet federal benchmarks that would unlock extra funding.

Over objections from the defendants’ attorneys, Superior Court Judge Jerry Baxter ordered all but one of those convicted immediately jailed while they await sentencing.

“They are convicted felons as far as I’m concerned,” Baxter said, later adding, “They have made their bed and they’re going to have to lie in it.”

The only one allowed to remain free on bail was teacher Shani Robinson, because she is expected to give birth soon.

Bob Rubin, the attorney for former elementary school principal Dana Evans, said he was shocked by the judge’s decision. “I felt it to be unnecessary and vindictive,” he said.

Prosecutors said the 12 on trial were looking out for themselves rather than the children’s education. Defense attorneys accused prosecutors of overreaching in charging the educators under racketeering laws usually employed against organized crime. The attorneys for some of the defendants said they will appeal.

The cheating came to light after The Atlanta Journal-Constitution reported that some scores were statistically improbable.

The months-long trial began in August with more than six weeks of jury selection, and testimony concluded in late February. The criminal investigation by the district attorney’s office lasted nearly two years and involved hundreds of interviews with school administrators, staff, parents and students.

District Attorney Paul Howard said it was the biggest and most complex case his office had ever handled.

“Our entire effort in this case was simply to get our community to stop and take a look at the education system,” Howard said.

Dessa Curb, a former elementary school teacher, was the one educator acquitted of all charges.

“I’ve prayed and I believed that this would be my outcome,” said a dazed-looking Curb, tears in her eyes.

Hall served as superintendent for more than a decade, which is rare for a big-city schools chief. She was named Superintendent of the Year by the American Association of School Administrators in 2009 and credited with raising student test scores and graduation rates, particularly among the district’s poor and minority students. But the award quickly lost its luster as her district became mired in the scandal.

In a video message to the staff before she retired, Hall warned that the investigation would probably reveal “alarming” behavior.

She added: “I am confident that aggressive, swift action will be taken against anyone who believed so little in our students and in our system of support that they turned to dishonesty as the only option.”