The analysis, it said, does not prove cheating but revealed a pattern of test scores in hundreds of cities that suggest widespread cheating.
The findings, based on the newspaper's analysis of test results for 69,000 public schools, come at a time when changes in education policy and teacher evaluations in many states put more weight than ever on test scores. The scores can decide whether educators keep their jobs and play a role in determining the amount of funds a school can receive or sanctions it can face.
Because of falsified scores, students who are struggling sometimes don't get the extra help they're entitled to, the Journal-Constitution said.
Cheating can come in the form of teachers erasing incorrect answers and replacing them with correct ones, giving students answers and providing improper one-on-one assistance during a test.
After being briefed on the results of the newspaper's analysis, U.S. Education Secretary Arne Duncan said in an e-mailed statement: "These findings are concerning. States, districts, schools and testing companies should have sensible safeguards in place to ensure tests accurately reflect student learning."
The federal government requires the testing but does not require screening scores or investigating those that are suspicious.
The analysis found that 196 of the nation's 3,125 largest school districts had enough suspect tests that the odds those results occurred by chance alone were worse than one in 1,000.