The report was published in Sunday's Atlanta Journal-Constitution.
The seven-month long investigation of testing data examined 1.6 million records from almost 70,000 public schools nationwide.
Suspicious score increases, high numbers of erasures and other irregularities were uncovered in about 200 school districts.
According to the investigation, "dozens" of mid-sized school systems, including those in Gary, Indiana, and East St. Louis, Illinois, exhibited "suspicious" tests in high concentrations.
