Secondary school headteachers say they are satisfied that the exams regulator is conducting a thorough and speedy investigation into complaints about a drop in GCSE English grades.
A meeting with Ofqual over the matter was "very constructive", said the Association of School and College Leaders (ASCL) which says it represents 80% of secondary school headteachers.
There are questions about how grade boundaries were set in a small number of English units over the year, the exams watchdog has admitted.
It said it will publish its initial report on Friday.
Teachers and local authorities have threatened legal action after it was revealed last week that the proportion of GCSEs awarded an A*-C grade fell for the first time in 24 years.
ASCL general secretary Brian Lightman said: "It is clear that (Ofqual) are determined to carry out a thorough investigation and we are very pleased that they have promised that they will issue a public, interim report by this Friday.
"We will be in regular contact with them this week and are continuing to assist their investigation in any way we can. We have already provided them with the evidence we have collected from more than 950 schools and had a thorough discussion about the technical issues surrounding the exams and grade boundaries.
"There appears to be a great sense of urgency and commitment within Ofqual to resolving this, and we were left in no doubt that they understand the seriousness of the situation for young people whose career choices are dependent on these results."
For justice to be done, young people who were marked down should have their grades reissued and based on January grade boundaries, Mr Lightman said.
Ofqual declined to comment on the meeting, saying it would not get drawn into a "running commentary" on the investigation.