There is widespread confusion about England's new GCSE grading system, says the exams regulator Ofqual.
Starting this summer, GCSE grades A* to G will be phased out in favour of grades numbered from nine to one.
However, around 70% of more than 400 parents and pupils surveyed by Ofqual did not understand the system.
"It is really important we explain the basics, like the fact that nine is the highest grade," said Chief Regulator Sally Collier.
Ofqual wants to raise awareness of the numerical grading system which starts this summer, with candidates who sit new more challenging English and maths GCSEs receiving a mixture of number and letter grades.
By the summer of 2018 a mix of numbers and letters will be awarded in an additional 20 subjects, with the letter system entirely phased out by 2019.
But according to the regulator's small survey, awareness is currently low - only 31% of secondary pupils and 30% of parents said they were clear how the new system worked.
Additional research with 50 human resources leaders revealed that less than half of them understood it, while among small businesses, this figure dropped to about a fifth, says Ofqual.
"We don't want there to be any surprises in summer 2017. It's really important that we spread the word that GCSE grades are changing from letters to numbers," said Ms Collier.
"Broadly the same proportion of students will get a grade four above as would have got a grade C or above in the old system," she explained.
Ofqual's publicity drive includes a series of online workshops for teaching staff in schools and universities.
The regulator is promising to widen the information drive to include employers in coming months.
The Department for Education says it has been working closely with Ofqual and with exam boards to communicate the changes.
A spokesman said the new numerical grades would be a clear signal to employers, colleges and universities that students have taken the reformed, more challenging GCSEs.
"Our GCSE reforms will create gold-standard qualifications that match the best education systems in the world and allow young people to compete in an increasingly global workplace.
"We continue to work closely with the sector to ensure they understand what the changes will mean for them when they come into effect later this year," said the spokesman.
Michael Turner, director general of the Joint Council for Qualifications which represents exam boards, said communicating the changes to students, parents educators and employers was "a huge task".
Mr Turner said efforts to spread the word would be "stepped up" in the run-up to the 2017 summer exams.
These reforms apply primarily to schools in England, although some pupils in Wales and Northern Ireland take GCSEs offered by English based exam boards. GCSEs offered by Welsh and Northern Irish exam boards are being reformed separately.
In Scotland National 4 and 5 qualifications replaced Standard Grades in 2014.
The survey was carried out for Ofqual by DJS Research in November last year.