The Atlanta Public Schools cheating scandal, outlined in stunning detail in last week’s state investigative report, started three years ago when an AJC reporter thought to herself that huge gains in curriculum test scores couldn’t be right. Here’s how the story has unfolded:

December 2008: An analysis by AJC reporter Heather Vogell and computer-assisted reporting specialist John Perry finds suspiciously high gains on state curriculum tests in schools in Atlanta and elsewhere in Georgia.

June-July 2009: A state examination uncovers unusual numbers of wrong-to-right erasures on summer retest answer sheets at four schools, including one in Atlanta. The state revokes the schools' status as having met federal standards that year.

October 2009: The AJC publishes a new analysis of Criterion-Referenced Competency Test scores that shows 19 schools statewide with highly improbable gains or drops on the test. A dozen were in Atlanta.

February 2010: The Governor's Office of Student Achievement analyzes 2009 CRCTs statewide, revealing suspicious erasure marks on thousands of tests from hundreds of classrooms. The state Board of Education orders 35 systems with suspicious erasures to investigate 191 schools statewide. Atlanta has the most schools flagged: 58.

March 2010: Atlanta school officials appoint a panel called the Blue Ribbon Commission to oversee the investigation. Many of the business and civic leaders on the panel have personal or professional ties to the district, raising questions about their independence.

August 2010: That commission's consultants find serious problems at only 12 of the 58 Atlanta schools. Questions were immediately raised about the approach and thoroughness of the group's final report.

August 2010: Then-Gov. Sonny Perdue appoints special investigators Mike Bowers, a former attorney general, Bob Wilson, a former DeKalb County district attorney, and Richard Hyde, who investigates cases for the Judicial Qualifications Commission, to examine possible cheating in Atlanta.

October 2010: Fifty GBI agents begin questioning Atlanta teachers and administrators about falsifying test results.

December 2010: The AJC reports that school district officials, including Atlanta Superintendent Beverly Hall, carried out a broad campaign to suppress mounting allegations of cheating. For months, officials kept secret a consultant's report that validated the AJC's initial analysis of testing irregularities.

January and February 2011: AJC articles report that district officials are accused of retaliating against employees who reported testing irregularities.

June 2011: The AJC publishes a story saying a letter by a lawyer for a former employee alleged Hall had ordered subordinates to destroy or withhold from the media investigative documents detailing "systematic" cheating on standardized tests.

June 30, 2011: The three special investigators deliver their scathing report to Gov. Nathan Deal. He releases it to the public on Tuesday.