Some students who sat NCEA exams on computers last year were mistakenly given fail grades, the Qualifications Authority says.
It said students who received a zero result for any of the digital pilot exams should talk to their teachers.
The Level 1 and Level 2 exams were offered in Classical Studies, English, and Media Studies.
It was reviewing the zero results and correcting students' records in cases where marks should have been allocated.
The principal of Pakuranga College, Mike Williams, said teachers realised there was a problem when they reviewed their students' exam papers.
"We were getting to the stage where it was a few in each class," he said.
"Every year with exams we do check, kids bring in papers if they think they didn't get a good result, we'll take a look at it, we'll work through with them whether they should go for a reconsideration.
"This one was too many one-off problems to be the old sort of mistake where a marker's just made a mistake."
Mr Williams said the error was a teething problem and did not have catastrophic effects on his students' results.
"At worst it would have been enough to tip them on to not achieving that standard, but that was just one standard in the mix of all the standards they were doing," he said.
The error was not picked up by NZQA's usual random check-marking process, the authority said.
"NZQA is reviewing any such results and, where marks should have been allocated, the students' record will be updated within the next few days.
"NZQA is contacting the relevant schools today and is looking into how this occurred."
The digital pilot exams were part of the authority's efforts to make all exams available digitally by 2020.
Students affected by the problem told RNZ they were initially disappointed by their results, but the experience had not eroded their faith in online exams.
Auckland student, Nancy, said she was surprised to see a not-achieved in her NCEA level 1 exam results.
"I was a bit shocked and a bit gutted because I thought I did all right on my exams," she said.
"At first I was kind of confused as to why it was a not-achieved. I spent a lot of time on that paper, so yeah, I was pretty disappointed."
Another student, Cindy, said she was disappointed and a bit angry to get a not-achieved grade in her English exam.
"I was very shocked because I had spent so much time with my teachers," she said. "I was really surprised about how badly I had done."
But both students said they would sit online exams again.
"The pros outweigh the cons and it's always good to have a trial and I feel like NZQA can learn from this," said Nancy.
"I'd rather do the digital exam because I think it's faster," said Cindy.