Schools said some pupils who were expected to pass the Media Studies National 5 qualification had failed.
Figures from the Scottish Qualifications Authority (SQA) show four out of 10 candidates failed the National 5 exam - even though the pass mark was lowered to 43 per cent.
One parent at a Glasgow school claimed she knew of several examples this year of youngsters getting a far worse grade than they had expected.
"This is very frustrating as some pupils who want to sit Higher media are not being allowed to continue as they don't have the relevant grade," she said. "Pupils and parents do not have any direct means of appealing and by the time that the schools do this it is too late for the pupils to pick up the subject at the Higher level."
However, the SQA says it had "robust mechanisms" in place to ensure candidates were challenged at the right level.
A spokesman for the exam body said: "SQA takes its responsibility to uphold the high standards of Scottish qualifications very seriously."
Overall, 60 per cent of the people who sat the National 5 in media studies passed. Pass rates varied across subjects, but the overall pass rate for National 5s was 81 per cent.