Teachers could be asked to submit predicted grades for pupils ahead of 2021 exams amid fears that thousands of pupils will not be able to take them.
School staff will be asked to draw up a rank order of pupils in each subject and send this to exam boards, under plans being considered by the regulator.
If a student is unable to attend an exam due to self-isolation or illness, the exam board would be able to award them a predicted grade partly based on the results of pupils above and below them in the rank order.
“It is one idea on the table,” a source said. “If someone can’t sit the exam, you look at the pupils above and below. If student B misses a paper, you look at student A and C and slot them in."
The Office of Qualifications and Examinations Regulation (Ofqual) is currently working on contingency plans for students who are self-isolating and miss some of their A-level or GCSEs.
Gavin Williamson has insisted that exams will go ahead because they are the “fairest way of judging a student’s performance” but concedes that these will need to be “underpinned by contingency measures”.
Downing Street officials are keen to avoid a repeat of this summer’s chaos, which saw a controversial algorithm ditched in favour of teachers' predicted grades following a national outcry.
Ofqual are understood to be studying options on how to award grades to students who have missed at least some of their exams.
Ministers are keen for pupils to sit at least one exam for Maths and English GCSE, but are more relaxed about other subjects.
Geoff Barton, general secretary of the Association of School and College Leaders, said that officials are “fixated” on the contingency plans for missed exams.
“There have always been special consideration arrangements for a child who can’t sit a paper because of a bereavement. If they miss one or two, special consideration can kick in,” he said.
“The real problem isn’t the exam, it is how to make sure they have covered the content. More and more headteachers are saying this cannot possibly be a level playing field.
"On the one hand you have people who haven’t missed much school at all and they would feel let down if they can’t take exams. Then you have people who have missed four or five of teaching already this term. How can the same exam accommodate them both?”
This week the Welsh exam regulator followed Scotland and proposed cancelling GCSEs next summer.
Qualifications Wales said that A-level exams should go ahead but with just one exam per subject, while GCSEs and AS levels should be awarded based on common assessments and coursework.
Earlier this month, the Scottish education secretary John Swinney announced that National 5 exams - which are equivalent to GCSEs - will not go ahead next spring and that awards will instead be granted based on coursework and teacher judgement.
Traditional Higher and Advanced Higher examinations, which are equivalent to AS and A-levels, would take place, he said, as long as public health advice states that it is safe.
Exams in England have been delayed by three weeks to allow more teaching time, and the Department for Education is due to announce additional measures to address “potential disruption” later this autumn.
An Ofqual spokesperson said: “We are considering a range of potential contingency options, alongside measures to maximise the opportunity for students to take their exams. We will say more before the end of the year."