A report commissioned by DC Public Schools Chancellor Kaya Henderson in March 2011 and released Wednesday said it didn't find evidence of widespread cheating on the 2010 DC Comprehensive Assessment System, tests administered under the controversial reign of former Chancellor Michelle Rhee. It did confirm cheating at the Crosby S. Noyes Education Campus.

But, as USA Today notes, the report, the product of a 17-month investigation, only actually focused on one school -- Noyes.

The investigation comes after a 2011 USA Today investigation found that several classrooms in Washington, D.C., had a high rate of incorrect answers erased and corrected, marks that often indicate teachers tampered with answer sheets. The allegations gained political traction because of Rhee's high profile, and helped shape about a national narrative about the consequences of high-stakes tests in America's schools.

According to the 14-page report, though, OIG found, through interviews, a dearth of evidence even at Noyes, so they concluded that there was “an insufficient basis to warrant” to investigate other schools flagged by erasure analysis. And as USA Today notes, investigators said they didn't inquire into further allegations because Henderson gave them "no additional evidence" of cheating.

Henderson, who commissioned the report by D.C.'s Office of Inspector General, said in a statement that she expects the Inspector General’s report “will put to rest claims about widespread wrong-doing.” But on Wednesday evening, Washington Post columnist Jay Mathews, who has long been critical of D.C.'s handling of the allegations, wrote in an online post that cast doubt on the latest report. "I think the truth of what happened in these tests will come out some day, but not because of the three inadequate investigations financed with D.C. tax dollars," Matthews wrote.

And the U.S. Education Department confirmed to The Huffington Post that its investigative arm is working on its own investigation.

At Noyes, the investigation found “definitive instances of testing impropriety” at Noyes, where proficiency rates climbed at a much faster rate than the average for D.C. schools from 2006-10. In 2008 and again in 2010, then-chancellor Michelle Rhee rewarded each Noyes teacher with an $8,000 bonus for boosting scores.

“It is disappointing that a handful of staff would think so little of their profession and of their students that they would do anything to compromise results. I am dismayed by the actions of these staff,” Henderson said in a statement. “And moreover, I am deeply saddened that their actions have compromised the integrity of our entire teaching corps and caused people to question the abilities of our 47,000 students.”

The report also included recommendations for improving test integrity at the district’s schools, many of which were already implemented during the 2012 testing session, according to Henderson. These included improved test monitoring, hiring a new investigative firm and increased security around testing materials.

Statewide 2012 DC CAS results released in late July showed growth in three subject areas across D.C.’s public schools. The district experienced gains in math -- up 2.8 percent from 2011 -- and science, up 5.3 percent. Reading scores also increased by 0.5 percent, reversing a two-year decline.

This year’s exams were seemingly administered without incident, unlike 2010 and 2011, when, once again, a forensic report revealed three Washington, D.C., schools cheated on the standardized test.

Last year, D.C. flagged classrooms for further investigation if they met two of three criteria: irregular wrong-to-right erasure ratios, unusual gains in test scores and scores within a classroom that don’t fit a bell curve. Of the 38 flagged schools, 23 were found to have some degree of test violations. Three of those 23 schools -- Martin Luther King, Langdon and Perry Street Prep -- received a “critical” designation and had their test results invalidated.

DC CAS scores are used in high-stakes decisions regarding teacher evaluations and hiring, which could have prompted teachers to change their students' answers.

UPDATE -- August 10, 11:00 a.m. AFT President Randi Weingarten has issued a statement, calling the Inspector General’s report “incomplete and inadequate” and claiming it “cheats kids and parents in the District of Columbia.”

“Cheating is a serious allegation. We owed it to the kids, parents, teachers and taxpayers of Washington, D.C., to launch a full-scale, thorough investigation, as was done in cities such as Atlanta,” Weingarten said. “By focusing on a single school, the Office of the Inspector General ignored the systemic indicators of cheating found in more than half of all schools in Washington, D.C. More than 103 schools were flagged for having statistically abnormal levels of wrong-to-right erasures.”

She went on to call into question the validity of the rising test scores in D.C. public schools, saying further investigation was needed to determine whether the inflated scores were the result of test tampering.

Also on HuffPost: