Former D.C. schools chancellor Michelle A. Rhee backed away Wednesday from her vehement criticism of a USA Today story on concerns about standardized tests during her tenure, acknowledging that some cheating may have occurred.In an interview with Washington Post education columnist Jay Mathews, Rhee said that some of her initial comments were “stupid.”

“You have got to have really strong test-security protocols at the district level and at the state level,” said Rhee, who contacted Mathews. “The vast majority of people will not cheat, but there will be exceptions here and there.”

Rhee, who was chancellor from 2007 to 2010, said the school system should ensure that after students complete D.C. Comprehensive Assessment System tests, answer sheets are not left in school offices where they may be vulnerable to tampering.

The issue emerged Monday when USA Today reported unusually high rates of erasures on answer sheets in more than 100 D.C. public schools from 2008 to 2010. At some schools, wrong answers were replaced by correct ones at rates too high to be random, according to statisticians consulted by the paper.

Rhee said in a statement Monday evening that USA Today was in league with “enemies of school reform” who believe that D.C. scores could not improve without teachers or students cheating. She said USA Today’s report was “an insult to the dedicated teachers and school children who worked hard to improve their academic achievement levels.”

Rhee has become a major national figure in education reform since her resignation last October. Her stature rests largely on her work in the District, where city and federal test scores rose during her tenure.

Earlier this year, Rhee faced criticism for claiming in 2007 on her resume that as a teacher in the early 1990s her students at Harlem Park Elementary School in Baltimore made significant gains on standardized tests. The record neither supports nor debunks such a claim.

Acting Chancellor Kaya Henderson, Rhee’s former deputy, announced Tuesday that she had referred questions about testing security in D.C. public schools to D.C. Inspector General Charles Willoughby. But she also expressed complete confidence in the findings of Caveon, a contractor the District hired to investigate erasures on the 2009 and 2010 citywide tests.

“DCPS has established procedures to ensure testing integrity and to flag any concerns,” Henderson said Tuesday.

Rhee described Caveon as “the best alternative we had at that time.”

Henderson did not return an e-mail message seeking comment Wednesday afternoon.