More than 500 students in Virginia just learned that their score on the Standards of Learning Civics & Economics test they took last spring rose when it was discovered that the answer to one question was incorrectly scored. For 224 students, getting credit for one more question meant the difference between failing the exam and passing.

Charles Pyle, spokesman for the Virginia Department of Education, said the question asked whether Virginia residents could register online to vote. The Virginia legislature passed a law in 2013, effective that same year, allowing online registration. But on the spring 2014 SOL test, a “yes” answer to the question was marked as it if it were wrong. When a teacher raised the question with officials later, the tests were rescored, Pyle said.

Pearson, the testing company that created the exams, recently sent out a letter (see below) to parents explaining the situation. According to Pyle, the responsibility for catching the mistake lay with the Education Department, which approved the question when it was written by Pearson, the state’s test vendor, before the law was changed in 2013.

According to Pyle, 224 students went from fail to pass/proficient and 384 students went from pass/proficient to pass/advanced. The tests are given to seventh- and eighth-graders and, Pyle said, are not high-stakes for students.

For teachers, the situation is a little murkier. Student achievement on the Standards of Learning exams is one of numerous measures factored into teachers’ evaluations. Pyle said it is unlikely that any single teacher’s evaluation would have been affected even if the mistake had not been found and the 224 scores that went from fail to pass had not been upgraded because single test scores have very limited overall impact.

Here’s the letter: