Confusion remains around the new GCSE 9-1 grading system, with many parents unsure that the change was a good idea.
Less than a week before the first grades are due to be published, a survey suggests that uncertainty remains among mums and dads.
The findings come as business leaders warned that students awarded the new grades are at risk of being disadvantaged if firms are confused by how they work.
Under the biggest shake-up of exams for a generation, traditional A*-G grades have been axed and replaced with a new 9-1 system, with 9 the highest grade.
English and maths - key GCSEs for all teenagers - are the first to move over, with other subjects following over the next two years.
The move has been introduced in a bid to allow more differentiation between students, particularly among the brightest.
But a new survey by Mumsnet and the Times Educational Supplement (TES) indicates that 32% of parents with a child of school age are still unaware of the new system.
Parents with secondary school children are more aware than those with primary-age youngsters (93% aware compared with 62% respectively).
Around a fifth (22%) thought that a 9 represented the bottom grade, not the top, with those with primary school children more likely to say this than those whose youngsters were in secondary school.
There was also confusion over what would be seen as a "good" pass - currently a C or higher is considered good, and under the new system a 4 will be broadly equivalent to a high C grade.
Of those with children in secondary school, 26% thought that a 4 would represent a pass under the new system, while 29% said it would be a 5.
Just over half (52%) of all of the parents questioned said they did not think a new grading system was a good idea. Among those with primary school children alone, this figure was 49%, and among those with secondary-age youngsters, it was 61%.
Mumsnet founder Justine Roberts, said: "You'd expect there to be some confusion about the regrading: it's a fairly major change, and it's not unusual for these things to take a while to be fully absorbed.
"But we've been surprised by how many parents still don't understand basic aspects of the system, and by how many think the shake-up will hinder their children's long-term prospects."
In an interview with the TES, Seamus Nevin, head of employment and skills policy at the Institute of Directors (IoD) warned that some employers may only know that GCSE grades have changed once they begin receiving CVs from pupils with the new results.
"They might think, 'What is this gibberish and what does it mean and how has it changed from previous grading systems?'", he told the TES.
The IoD said that since the interview was conducted, it has been working with government and others to communicate the changes.
"Any major change like this needs to be communicated effectively to ensure that employers understand what this means for their recruitment," Mr Nevin said.
"Many businesses, especially SMEs (small and medium enterprises) who make up the bulk of UK employment, will only begin to engage with these changes after the first CVs with the new grades land on their desk.
"That risks disadvantaging students if bosses are confused by the metric."
Exams regulator Ofqual has said that its films about the changes have been watched millions of times.
A Department for Education spokesman said: "The Government' s new gold-standard qualifications are a culmination of a six-year process of curriculum and qualifications reform and we have worked with Ofqual to issue a wide range of resources since 2014 to help raise awareness of the new grading system."
He added: "Almost two-thirds of employers are aware of the new GCSE grading system, and we will ensure that engagement continues."
:: The Mumsnet poll questioned 1,014 parents with at least one school-age child, between July 13-28.