Private schools awarded top grades to 70% of their pupils’ A-level entries as part of a record-breaking set of results on Tuesday, increasing the attainment gap with state schools in England to the widest in the modern era.

Black pupils and male pupils were outperformed by their peers, with the gender gap reaching its highest level in 10 years as teacher assessments appeared to boost female students’ performance.

The more generous results awarded by teacher assessment led to celebrations by school leavers accepted on to university courses in the autumn, but the head of the exam regulator, Ofqual, vowed that formal exams would return next year.

While the national results in England, Wales and Northern Ireland showed that 45% of entries were awarded A* and A grades, the use of teacher-assessed grades in place of exams this year disproportionately benefitted those at independent schools, where the proportion of A* and A grades rose nine percentage points to 70%, compared with six percentage points elsewhere.

Secondary comprehensive schools’ A and A* rate rose to 39.3%, or 41.9% for academies.

Figures published by the Joint Council for Qualifications showed there was a more than 20 percentage point gap in the proportion of top grades between independent schools and state schools in 2019, the last year when formal exams were taken.

This year the gap widened to 31 percentage points between independent schools and comprehensives in England, while the gap between independents and state sixth form colleges was even wider, at 35 percentage points.

David Robinson, of the Education Policy Institute, said the widening gap could be due to the greater disruption and lost learning time endured by many groups, with the chances of black students gaining A* or A grades declining alongside those from disadvantaged backgrounds.

“Lost learning has affected different groups differently and that’s probably why students from disadvantaged backgrounds are among the most affected,” Robinson said.

Private school pupils might have also benefitted from parental pressure on teachers, while the higher levels of prior attainment seen in independent school pupils was a contributing factor.

“Even controlling for prior attainment, students from disadvantaged backgrounds were worse off by at least a tenth of a grade compared to those from more affluent backgrounds, even among students with the same GCSE grades,” Robinson said.

Kate Green, the shadow education secretary, said that while students deserved to be congratulated for their hard work, “the Conservatives’ chaotic last-minute decision making has opened the door to unfairness”.

She added: “The increase in A grades is 50% higher among private schools, while black students, students on free school meals and in areas of high deprivation, are being increasingly out-performed by their more advantaged peers.

“The government’s measly recovery plan will see half a million students leave school this summer without any support to recover lost learning or boost their wellbeing.”

Analysis published by Ofqual said there were “lower outcomes” for black candidates, those on free school meals, and those with a high level of deprivation.

Simon Lebus, the interim chief regulator of Ofqual, defended the process used, following the scrapping of national exams in January by the education secretary, Gavin Williamson.

Lebus said it would have been unfair for students to have sat exams because of the “significant disparities” in teaching between schools before and during lockdown.

He said: “The pandemic will have had different impacts on students’ opportunities to learn, and the mechanisms we normally use to secure standards over time have not been deployed this year.

“We expect to get back to exams and formal assessments next year because although exams are not perfect they have proven to consistently be the best way of assessing what a student knows, understands and can do.”

Lebus said Ofqual and the Department for Education would announce early in the autumn a joint consultation on how exams would proceed next year.

But experts warned that A-level candidates, by 2022, would have faced significant disruption to their learning over the past two years.

Lee Elliot Major, professor of social mobility at the University of Exeter, said: “It is deeply concerning to see widening socio-economic divides in this year’s A-level results, confirming our worst fears – the pandemic has exacerbated educational inequalities outside and inside the school gates.

“The government urgently needs to set out its plans for a return to a national exam system from next year that is fair to all pupils irrespective of what school they attend or home that they come from.”