This involves pupils disadvantaged by circumstances being awarded up to an extra 5% of the maximum marks.
Milk deliveries have also been disrupted, with tankers struggling to reach dairy farms.
Some farmers have had to dump supplies as few have storage facilities to hold more than a day's stock.
Easyjet has cancelled about 30 flights at airports including Gatwick, Liverpool, Belfast and Stansted, while Norwich Airport has been closed.
British Airways said passengers should check the status of their flight before leaving for the airport.
Overnight it had asked passengers on some flights arriving at Heathrow's Terminal 5 to leave without their luggage, with bags being sent on to them later.