A U.S. senator from Georgia and a national teacher union leader on Sunday called for investigations into possible cheating in school districts cited in an investigation into suspicious test scores by The Atlanta Journal-Constitution.

The newspaper reported Sunday that 196 of the nation's 3,125 largest school districts had a high degree of suspicious results on standardized test scores, which could point to instances of cheating.

The results of the AJC's analysis of test scores from all 50 states do not prove cheating. But several officials said these school districts must now take the AJC's statistical analysis and find out whether cheating is occurring in their schools. Extreme swings in test scores occurred in several major urban school systems, including Baltimore, Dallas, Detroit, Houston, Los Angeles and Mobile County, Alabama. Suspicious scores were most likely to appear in urban and rural school districts that served mostly poor children.

Beyond that, the AJC report reignited the national debate over standardized test scores as the primary measure of improving public schools. While some educators defended the practice, stressing that cheating is a moral choice, others said teachers have come under too much pressure to get results.

For now, the school districts identified in the AJC analysis must do their own inquires into potential cheating, officials said.

"The indications of the report are troubling, to the point where these systems must follow up and see whether there is in fact impropriety," said U.S. Sen. Johnny Isakson, R-Georgia, a member of the Senate Committee on Health, Education, Labor and Pensions.

If these districts fail to do so, Isakson said the governors of the states should intervene. And should they drop the ball, "there may be a federal interest ... I don't think Congress could look the other way."

Randi Weingarten, president of the American Federation of Teachers, one of the two major teachers' unions, told the AJC that the findings suggest the need for more investigation in many school districts across the country.

"It should go to another level," she said, such as systematic analysis of erasures on test papers and, if necessary, investigations by law enforcement officers -- both of which helped prove widespread cheating in the Atlanta Public Schools.

Isakson said the handling of Atlanta's school cheating  should serve as the model for the rest of the country. Then-Gov. Sonny Perdue,  dissatisfied with the school district's inquiry, appointed his own special investigators. That cheating scandal began with the AJC doing the same type of statistical analysis it later employed on a national level.

One special investigator, former Georgia Attorney General Michael Bowers, said he has long expected that test scores have been artificially inflated around the country.

"There needs to be a very close look at the effectiveness of standardized testing, especially as it relates to certain children who come to school without the sufficient home life to succeed," Bowers said. In particular, he pointed to some children in poor and urban areas.

But Isakson said it's wrong to condemn the testing. "Cheating is a moral failing, not the result of a test," he said. "If you don't measure your progress, you won't know what direction you're moving in."

The AJC story was picked up by more than 300 news outlets around the country, including the Huffington Post, ABC News, the Washington Post, NBC Nightly News and MSNBC. Several news outlets in areas identified in the report ran their own stories, including The Tennessean and The Houston Chronicle. The story also created a social media buzz, generating several hundred tweets on Twitter and numerous mentions on Facebook.

Reaction by districts identified in the AJC's analysis varied widely. Some said they would initiate deeper reviews, while others challenged the findings and defended their schools' integrity. The newspaper analyzed test results for 69,000 public schools and found high concentrations of suspect math or reading scores in school systems from coast to coast.

After reviewing the AJC's findings, the superintendent of the Houston school district told the Houston Chronicle that he will review the AJC results with principals and may put in place additional test monitors.

In 2002, Houston was the first winner of the Broad Prize, which has become the most coveted award in urban education. The Eli and Edythe Broad Foundation praised Houston's intense focus on test results. More recently, Houston has been among the leaders in tying teacher pay to student test scores.

But twice in the past seven years, the AJC found, Houston exhibited fluctuations that had little chance of occurring except through tampering. After the 2011 testing, for instance, the district substantiated nine cheating accusations and fired or took other disciplinary action against 21 employees.

"I want you to know that the [school district] takes these allegations seriously and does not tolerate cheating," said Houston Superintendent Terry Grier. He said the district has done its own cheating investigations and put safeguards in place.

The chief executive of the Baltimore schools, Andres Alonso, pointed out that the newspaper’s analysis found extreme changes in his district that were mostly decreases in scores that followed a heightened effort to prevent cheating. Officials found cheating in three Baltimore schools in recent years, and are investigating more than a dozen others. Few districts have attacked cheating as aggressively as Baltimore.

“We were so zealous in our attack on cheating because we wanted to make that point without leaving a shadow of doubt,” Alonso told the AJC.

Nashville school officials challenged the newspaper's results as flawed, asserting in a statement that "Nashville has no place in the story." The officials pointed to their high rate of children moving in and out of their district, as well as its high percentage of students learning English.

AJC Editor Kevin Riley stood by the results.

"We believe in our methodology and are transparent about it," Riley said. "In the case of Nashville, we're looking into their concerns. We found many districts nationwide that share many of the characteristics Nashville cites -- high mobility, a lot of students enrolled in English as a second language course, for example. Chicago is one; as was LA in most years. Amarillo, Texas, also has a large number of students learning English. But relatively few cities show the unusual results we found in Nashville."

Some parents praised the AJC analysis for its national sweep, and said they hoped it would further discussion on federal education policies.

"If there is widespread cheating going on in numerous communities across the country, as this report suggests, that adds to the concerns about how[No Child Left Behind] and its emphasis on standardized test scores have affected our public education system," said Dori Kleber of Dunwoody, who has two children in DeKalb public schools. "If the AJC's report leads to more scrutiny of the effects of NCLB, I think that would be a good thing for all schools."

Staff writer Alan Judd contributed to this report.