The existing flexibility in the exam system should enable students and teachers to cope with the disruption caused by the volcanic ash cloud.

The Joint Council for Qualifications, which represents the seven largest exam boards, said it was “sympathetic to those teachers and students who are unable to return to the UK as a result of the current international flight situation”.

Language oral examinations and other practical exams can be taken this week. There are also deadlines looming for coursework to be submitted. But many of the practical assessments have no fixed date and can be moved as long as they are taken by a certain deadline - although schools should inform the awarding bodies of changes they make.

The AQA exam board is expecting schools to run assessments before mid-May in music, ICT, performing arts and modern foreign languages. It has recommended that schools try to reschedule internal assessments and offered to help rearrange visits from visiting moderators or examiners. Similarly, the OCR exam board has said it is looking at the issues on a case-by-case basis.

In contrast, there will be no rescheduling of the written papers for GCSE and A-levels, which are due to start on May 17.

Ofqual, the exams regulator, said it was monitoring the situation. If students are likely to miss any exams that cannot be rescheduled, they can apply for special consideration.

But some schools have managed to set work online. Wellington College in Berkshire has been running lessons and tutorials by internet, email and phone.