Miscalculated scores, flawed questions and other errors on standardized tests have become near commonplace in public schools across the country, according to a new investigation by The Atlanta-Journal Constitution.

Repeated failures in quality-control measures have allowed mistakes to keep happening even as testing took on a more crucial role for students and teachers, the newspaper found. In some cases, students have been initially denied diplomas or entry into special academic programs because of incorrect scores.

The findings expose significant problems in the execution of the landmark No Child Left Behind Act of 2001, which sought to use test scores to hold schools publicly accountable for students’ academic performance. The newspaper has previously reported other problems with standardized testing, exposing widespread cheating in Atlanta Public Schools. A follow-up investigation in 2012 revealed nearly 200 school districts nationwide had high concentrations of suspect scores.

In the current year-long investigation, the AJC’s Heather Vogell studied test design, delivery and scoring and reviewed statistical reports on the quality of more than 92,000 test questions given over two years to students in 42 states and Washington, D.C.

The investigation revealed that almost one in 10 tests nationwide contained significant blocks of questions that were likely flawed. Such questions made up 10 percent or more of those tests — threatening their overall quality and raising questions about fairness.

“I think that’s just the bottom line,” said Matthew Johnson, a professor at Teachers College in New York City who advised the AJC on this project. In some states, he said, “there is no quality control, or very little.”

Subscribers can read the full story and more in Sunday’s Atlanta Journal-Constitution and on MyAJC.com. Not a subscriber? Click here and you can sign up for a one-day pass for 99 cents.