A grassroots group of more than 5,000 heads is warning it is “neither realistic nor workable” to catch up in full by next summer.
They are calling for reduced content or to have some “open book” exams where students can use text books.
The exam watchdog Ofqual has suggested removing some practical parts of exams.
West Sussex head teacher Jules White is the organiser of the Worth Less? campaign group, which originally formed over school funding shortages.
The network of heads is now raising concerns about trying to run next year’s exams with few changes, when many pupils have been out of school for so long and when there is the risk of more disruption from local lockdowns.