The Maine Department of Education is working to resolve an error in standardized test score data sent to schools that contains graphics that incorrectly show how students performed compared with their peers.

Results of the Maine Educational Assessment, a standardized exam given to students in grades three through eight and high school juniors, have not yet been released publicly, although some school districts have released them to parents.

On Tuesday, the department sent letters to school districts advising them of a problem with information indicating how students performed relative to their peers.

The data is correct but graphics showing the percentiles that student scores fall into are not, said department spokeswoman Kelli Deveaux in an email. She said the numbers printed on student reports overlap, so a student’s specific score may show up in two different percentiles.

The issue prompted at least one Maine school district to send a letter to parents Tuesday advising there may be “inconsistencies” with their children’s scores.

“This is a state-wide issue and is being handled at the state level,” said Cumberland-based School Administrative District 51 acting Director of Academic Services Susie Robbins in a letter to parents. “It is our understanding that these discrepancies are minor, if any.”

The department is working with its vendor, Focal Point K-12, which said it expects the glitch to be resolved by the close of school Wednesday, Deveaux said.

“I realize many districts have already shared (results) with families,” said Nancy Godfrey, assessment coordinator for the department in the letter sent to districts Tuesday. “Please know, the team makes every effort to ensure the data we provide our vendors and subsequently our vendors provide publicly is accurate. We apologize for the inconvenience this may cause and for confusion or additional questions you may receive from families.”

The Maine Educational Assessment, or MEA, is based on English and math test scores for third through- eighth-graders and SAT scores for high school juniors.

Science results are from a test given to students in fifth and eighth grades and to high school juniors.

Data is typically released in late fall, though there is no established timeline for its distribution.