Letters are being sent home to 26 Carson City students, notifying them that they passed Nevada's high-school proficiency exam. They were originally told they had failed.
The company responsible for the error may face a $400,000 fine.
A scoring error left 736 Nevada high school students believing they had failed the math portion of the test. Nevada students must pass a reading, writing and math portion to graduate from high school.
"This error in reporting means we have failed in our responsibility to students," said State Superintendent Jack McLaughlin. "We are here to serve students, to ensure that they have the opportunity to succeed academically and to provide them with the opportunity to demonstrate achievement."
The test is developed, scored and reported through the Harcourt Educational Measurement company. The error was disclosed to the State Department of Education on July 25, indicating 468 10th-graders and 268 11th-graders from 83 Nevada high schools received mistaken results.
Seniors took a different portion of the test and were not affected.
Carson High School counselors sent letters to 16 sophomores, nine juniors and one adult student to let them know they passed.
"I'm very happy for these students who thought they failed this test," Superintendent Mary Pierczynski said. "They passed it."
The mistake was made when initial reporting required students to answer 42 math questions correctly to pass as a result of an improperly formatted file. Students needed to answer only 41 questions correctly.
"There is no excuse for this type of reporting error," said Paul La Marca, assessment director for the state board of education. "It is egregious and calls into question the capacity of Harcourt to serve Nevada's students."
Although McLaughlin commended the contractor for disclosing the error promptly, he said the future relationship with the company is unclear.
Juniors and seniors were given another opportunity to take the exam in July. Three of the juniors who already passed the test took it again.