However, many were closed to other pupils. In West Yorkshire, 200 are shut. Across Wales, at least 440 are closed - the majority in the Valleys.
Exams watchdog Ofqual said it had not been informed of any centres being unable to hold exams, although some may have made alternative arrangements such as switching pupils to alternative venues or estimating grades.
Some rural communities remain cut off, while others are coping with power cuts, increasing numbers of potholes and cancelled rubbish collections.
Freezing conditions are causing water pipes to split. Yorkshire Water has been taking 160 calls a day about the problem and has 75 teams repairing them.
Heating oil firm Total Butler has said it is struggling to meet demand from households, despite government permission for its drivers to work longer hours.
The Federation of Small Businesses says bad weather is costing the economy £600m a day.
It is backing an internet campaign to cancel half-term holidays for schools that have closed as compensation for staff having taken time off work to look after children.
Meanwhile, police officers in Oxfordshire have been warned that "tobogganing on duty, on police equipment and at taxpayers' expense is a very bad idea" after video footage showed a group watching as one slid downhill on a riot shield.
Airports are open after a day of delays and cancellations caused by snow closing runways at London City, Birmingham International, Southampton and Cardiff.
Nearly 300 flights were cancelled at Heathrow on Wednesday. Gatwick, where flights were suspended for 12 hours, is experiencing knock-on delays.
Most train operators are running normal timetables again, after serious disruption, according to National Rail. Four Eurostar services are cancelled
East Coast services in Scotland and between Leeds and London are still disrupted, while First TransPennine Express is operating replacement buses in north-east England
In Scotland, a number of roads in the Highlands remain closed because of snow, along with several routes over high ground in Wales.
The A66 in Cumbria and the A628 in Derbyshire remain shut
Hospitals are dealing with many more fractures as people slip on ice, with the Queen's Medical Centre in Nottingham seeing "unprecedented" numbers and 97 people treated for broken bones at Antrim Area Hospital in a week.
The Royal Berkshire Hospital in Reading said nearly a quarter of those admitted to casualty last week had fallen in snow.
Yorkshire Ambulance Service reported a four-fold increase in calls on Wednesday morning, with black ice a hazard across the region.
Councillors in Leeds say they have only enough salt to grit primary roads five more times - lasting about two days - while neighbouring Kirklees has enough for just four coverings.
Gordon Brown has said the government is confident it will be able to "maintain the road network".
Thames Valley Police officers use their riot shields to sledge in the snow
He said one UK salt producer was stepping up production and imports were expected in the coming days.
The prime minister also pledged to review the arrangements for keeping Britain moving in severe weather.
The Highways Agency and councils have already cut salt use by half - up from the 25% agreed last week - to protect supplies.
And no councils in England or Wales have run out of salt, despite facing freezing conditions for a third week, according to the Local Government Association.
British Salt director David Stephen said up to 30 authorities turned down the offer of cut-price de-icing salt last April.
The AA predicts the thaw will reveal a 30% increase in the usual number of potholes. Councils spent £67m filling in almost 1m last year, figures suggest.
AA President Edmund King told the BBC: "If they are not filled in, you can pay out more in compensation. Last year, £47m was paid out in compensation for people's vehicles damaged, bicycles, motorcycles, or indeed injuries."
The Environment Agency said there might be an increased risk of flooding in some areas over the weekend due to predicted heavy rain and the partial thawing of snow.
It said the small amount of water from melted snow was not expected to cause significant flooding problems if it "happens steadily over many days" but with the forecast rainfall, this thawing could "happen more quickly".
BBC weather forecaster Darren Bett said the only snowfall on Thursday would be in parts of Scotland, including Perthshire and Glasgow.
Wales would be very cold with icy conditions, Northern Ireland dry and some rain or sleet was likely in Dorset and southern England, "adding to the icy mix", he said.
Temperatures for many parts would be 1 or 2C (34 or 36F), he added.
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