The chief qualifications regulator in England, Sally Collier, said that this year’s A-level and GCSE students would not suffer from being the first to take the new, tougher, exams.

Collier, head of the Ofqual assessment watchdog, sought to reassure parents and students – as hundreds of thousands of families anxiously awaited the publication of this summer’s A-level and GCSE results – saying that although the new exams were more testing, the final grades would be fairly distributed and in the same way as in previous years.

This Thursday (16 August) the results for A-levels will be published, including more than 20 of the tougher versions of the exam. They will be followed by GCSEs the following week in which the familiar letter grades from A-G are replaced by the numbers 9-1 in many subjects.

Dismissing suggestions that students taking the exams this summer were “guinea pigs”, Collier said: “There has been commentary that the exams were harder – and, truly, students have been studying more challenging content. That was the government’s policy intention in reforming these qualifications. But the approach we adopt, known as comparable outcomes, means that students aren’t disadvantaged relative to students in previous years just by being the first cohort to sit the new qualifications.”

For some parents it may be the first time they have seen letter grades replaced by numbers in GCSEs, with 9 representing the previous top A* grade and 1 equating to G. Instead of C as the acknowledged grade for a good pass, the reformed GCSEs will award a 4 or 5, with the higher number regarded as a “strong pass”.

“All things being equal, a student who would have got a C or above in their GCSE last year will get a four or above this year,” Collier said.

Last year students sat reformed GCSEs in English and maths for the first time, while this summer students were tested on a wider range of 20 reformed subjects.

Pupils in England this summer have sat reformed exams spanning 20 subjects. Photograph: David Davies/PA

Ofqual and the exam boards in England use a process known as comparable outcomes to fix the proportion of grades awarded in both qualifications based on prior attainment. At A-level the outcomes are set using the year-groups’ GCSE results two years’ previously, while at GCSE the proportions are based on tests taken at the end of primary school five years ago.

“Our message is one of continuity,” Collier said. “As standards are set in new qualifications this summer the use of comparable outcomes means that if the students taking them are of similar ability to those taking them last year then national outcomes in the reformed qualifications will be steady.”

The reformed qualifications – part of the overhaul ordered by Michael Gove as education secretary – mainly rely on exam results for determining a final grade, rather than classroom assessment carried out by teachers. Meanwhile, the halfway module for A-levels, the AS-level exam, has been decoupled, meaning that A-level grades no longer include AS results.

The reforms only apply to A-levels and GCSEs in England. The results for those in Wales and Northern Ireland will be published at the same time but they are regulated differently and are unaffected.

Collier said Ofqual used social media to monitor allegations that the tougher exams were causing greater amounts of stress for this year’s pupils, comparing posts this year to last year.

“The pattern of social media activity relating to exams, over the exam period, is extraordinarily similar,” Collier said. “After every single subject, I don’t think we had a single exam where the vast majority or the majority of students came out and said ‘this was impossible’ or ‘this was too hard’. Actually, the comments were very, very, balanced.”

The exam overhaul is thought likely to benefit boys, who appear to do better under stressful exam environments, rather than girls, who in the past did better from longer periods of assessment.

Alan Smithers, a professor of education at Buckingham university, noted that boys improved their results relative to girls in each of the 13 reformed A-level exams last summer, and expected to see a similar performance this year.