Teachers in 18 District classrooms cheated on high-stakes standardized tests last year, according to a report released Friday by the Office of the State Superintendent of Education.

The findings come one day after journalist John Merrow published a 2009 document that raised questions about whether the District adequately investigated past cheating allegations.

School officials maintain that no widespread cheating has occurred, pointing to multiple investigations over the past two years that found only isolated violations. They said Friday’s report is more proof that there is no systematic problem in the District.

“The majority of the schools are playing by the rules,” said Jose Alvarez, chief of staff for the state superintendent of education.

But D.C. Council member Kenyan R. McDuffie (D-Ward 5) — who has criticized previous investigations — said the violations might be a sign of a wider problem. He urged the District to consider whether one of its signature reforms — tying teacher evaluations to test scores — might be motivating adults to cheat.

A consultant’s four-page memo on D.C. schools.

Beneath the back-and-forth is a debate about whether standardized tests, increasingly used to judge teachers and schools, are a reliable indicator of student progress.

D.C. test scores have come under increasing scrutiny since revelations that more than 100 schools had unusually high numbers of erasures of wrong to right answers from 2008 to 2010. Such erasures are an indication that cheating may have occurred, but they are not proof.

The District’s annual standardized test, known as the D.C. Comprehensive Assessment System, was given to students in 2,688 classrooms last spring. The OSSE flagged 41 classrooms in 25 schools for extra scrutiny based on odd patterns, such as wrong-to-right erasure marks, unusually big gains or drops in students’ scores, and unusual score patterns.

Then a management consulting firm, Alvarez and Marsal, visited schools and interviewed students, teachers and administrators. (Jose Alvarez is not connected with the consulting firm.)

The 18 classrooms found to have critical violations were in 11 schools: seven traditional schools and four charter schools. The test-tampering included providing students with answers, reading test questions aloud and encouraging students to reread specific questions. Scores on the 2012 tests at those schools will be invalidated. For six of those schools, that will trigger additional oversight of academic programs and interventions for struggling students.

The seven traditional D.C. public schools at which cheating was detected are two preschool-eighth grade campuses — Brightwood and Winston — and five elementary schools: Beers, Hendley, Kenilworth, Langdon and Miner.

The four charters are Arts and Technology Academy, Community Academy-Amos I, Hope Community-Lamond and Meridian.

Scott Pearson, executive director of the D.C. Public Charter School Board, said the board will ask each school to explain how it will address the violations. The charter board will address further actions against schools at its May 20 public meeting.

D.C. Public Schools Chancellor Kaya Henderson said she would take appropriate disciplinary measures after reviewing OSSE’s report.

“We do not tolerate cheating at DCPS,” Henderson said. “We take every allegation of testing impropriety seriously, investigate accordingly and take personnel action when warranted.”

But some question whether Henderson and her predecessor, Michelle A. Rhee, have pursued cheating allegations aggressively enough.

In 2009, a consultant for D.C. Public Schools warned that it might have had widespread cheating on standardized tests the previous year, according to a memo obtained by Merrow and published Thursday on Merrow’s blog.

The four-page memo, marked “confidential,” was written by consultant Fay G. “Sandy” Sanford and addressed to a senior staffer of Rhee’s. It contains no proof that cheating occurred, but it said erasure-rate data indicated that nearly 200 teachers at 70 schools could have been “implicated in possible testing infractions.”

The public release of the document has raised questions about why Rhee decided not to investigate test scores in 2008 — her first year on the job, when many schools made impressive gains.

Subsequent investigations by private consultants and local and federal inspectors general found no evidence of widespread cheating, but they also did not fully examine the 2008 scores.

Neither Rhee nor Henderson recalled receiving or discussing the memo. A spokeswoman for Henderson said that the testing company found that there was not enough information available to conduct a further investigation.