Universities are being urged to give disadvantaged students who narrowly miss their required A-level grades “additional consideration” after research laid bare the disruptive impact of Covid in the run-up to exams.

One in five A-level students (21%) who applied to university missed more than 20 days of school this year due to Covid disruption, while a third have missed 11 days or more, according to research by the Sutton Trust educational charity.

Amid concern that the most disadvantaged have been hit the hardest, almost three-quarters of teachers (72%) were worried that the attainment gap between the most and least disadvantaged will increase. Almost half (45%) of the 4,000 teachers polled thought the adjustments to exams designed to mitigate the impact did not go far enough.

The Sutton Trust chief executive, James Turner, said: “Today’s research highlights that the impacts of the pandemic on education are far from over – and the consequences are still being felt among young people and their teachers.

“As we approach results day and a more competitive university admissions cycle than ever, we must make sure that poorer youngsters have a fair chance to succeed.

“Universities should give additional consideration to disadvantaged students who have just missed out on their grades and make sure recent gains in widening access to higher education are not lost.”

The research shows anxiety is high among students who are the first to sit exams for two years, at a time when the government is seeking to rein in grade inflation and competition for university courses is intense with record numbers of applicants and fewer places on some of the most popular courses.

Just half of the 430 students (52%) who took part in the Sutton Trust survey felt this year’s exam arrangements took the impact of the pandemic sufficiently into account and 62% felt they had fallen behind with their studies compared with where they would have been without the pandemic. Almost two-thirds (64%) were worried about their grades, compared with 58% last year, and applicants from working-class backgrounds were more likely to be concerned.

Dr Mary Bousted, joint general secretary of the National Education Union, said: “It is these students [from disadvantaged backgrounds] who will suffer most from the new rationing of university places.”

Meanwhile, analysis by PA Media of figures published by the Department for Education (DfE) showed there were almost 13,000 school exclusions in England last year due to breaches of coronavirus rules.

Of 12,965 exclusions for “wilful and repeated transgression of protective measures” from schools in England in the last academic year, 12,888 were temporary and 77 permanent. The Covid breaches included non-compliance with social distancing and causing distress by purposefully coughing near to others.

The DfE was contacted for comment.