Officials in Maryland’s second-largest public school system blamed computer glitches for grade and credit errors on thousands of students’ report cards in February.

“We do have a lot of worried parents and students,” said Brian Porter, representative for the Montgomery County Public Schools.

The school system has about 129,000 students. Problems affected 66,288 report cards produced for secondary students.

Officials said grading or credit errors affected about 3 percent of the report cards, while 15 percent of the report cards contained formatting errors.

“It reflects lingering problems with a new student information system we began using last fall,” said Porter, though he would not say which system the district was using.

The formatting problems included grades and other information that was not printed in the appropriate columns.

Officials said the errors began surfacing when report cards were distributed Feb. 15. High school teachers routinely inform students of their grades before they are submitted, so students were surprised when grades were missing or different from those anticipated, officials said.

Some students did not receive credit for classes taken. Others failed to have all course grades included in the tabulations of their grade point averages.

The problem was potentially most worrisome for seniors who are applying to colleges and universities. The grade omissions could have degraded the quality of the transcript information submitted to the colleges.

Officials with the school system issued corrected transcripts and report cards on different colored paper stock to make up for the errors.

“We’ll contact the schools [colleges] if necessary,” Porter said. However, he said, most seniors already have received acceptance letters from colleges.