THE FIRST “erasure analysis” of D.C. student scores on standardized tests in 2008 came with a warning not to use it as proof of cheating.

“We advise,” wrote an expert from McGraw-Hill, “against concluding that cheating behavior may have occurred in these schools, based on these analyses.” A separate security firm that investigated 2009 and 2010 test scores was similarly careful in outlining legitimate factors that could account for high erasure rates.

Those words of caution have been ignored in an effort to question reforms initiated by Michelle A. Rhee during her tenure as D.C. schools chancellor.

Whether it be a subtle nudge to a student to look again at a question or the overt changing of answer sheets, cheating cannot be tolerated. That’s why Ms. Rhee, serving as chancellor from 2007 to 2010, brought in a high-priced security firm to monitor school testing protocols and investigate instances of suspicious activity. It’s why Kaya Henderson, Ms. Rhee’s successor, asked for an independent investigation of school practices after USA Today described last year what it considered unusual numbers of wrong-to-right erasures on D.C. Comprehensive Assessment System tests in more than 100 schools.

Results of that investigation by the city’s inspector general, with assistance from the U.S. Education Department, are pending. Some critics see no need to wait in pronouncing on what they portray as a major scandal. Post education columnist Jay Mathews, always careful to point out that his editor wife conceived and oversaw the USA Today project, has been especially critical, advocating that the city undertake rigorous interrogation of principals, teachers and even students. A recent column in the New York Times suggested that Education Secretary Arne Duncan should avoid being seen with Ms. Rhee and that Ms. Henderson ought not to have been invited to speak at this week’s conference by the department’s National Center for Education Statistics.

Ms. Henderson did speak, and she used the occasion for some apt observations. “We turn tests, which are in place so that we can celebrate students’ successes and address areas of concerns, into a game for adults,” she said. Ms. Henderson called for national standards to guide investigations of suspected cheating. Any fair review of the District would acknowledge its efforts to ensure the reliability and accuracy of testing. That includes rigorously requiring central office staff and third parties to observe testing; establishing a confidential tip line that allows concerned parties to report wrongdoing; using an independent contractor to investigate suspected cases; and swiftly punishing those found to have acted improperly.

We’re willing to wait for the investigation findings. But even if it reports instances of inappropriate activity, this fact will remain: Since 2008 — the year in which many of the concerns seem to be centered — the school system has administered the D.C. tests three times and the National Assessment of Education Progress (NAEP) twice. Cheating is not alleged in the NAEP tests; yet they and the D.C. tests have demonstrated similar progress in student achievement. Indeed, on NAEP, D.C. schools were the only urban district to make gains in math and reading in both the fourth and eighth grades between 2007 and 2009. That record can’t be erased.