Many schools in England and Wales are remaining closed for a second day following the heavy snowfall - to the annoyance of some parents.
Decisions about school closures are taken locally
Birmingham City Council said all its 400 schools would stay shut.
In Buckinghamshire, some schools felt they had no option after the county council suspended school bus services.
Some parents, forced to take time off work to care for their children - or pay others to do so - feel that some schools have been over-reacting.
Margaret Morrissey of the National Confederation of Parent Teacher Associations said parents would be angry because they could not take children away for holidays in term time - yet schools could spring closures on them at the last minute.
"All of a sudden it's OK to take them away because the weather is slightly inclement," she told BBC Radio 4's Today programme.
"It does sort of make you wonder when you see pictures of them in the evening news flying down hills on pieces of cardboard with nothing on their head: which was more dangerous, going to school a bit early, to take a safe and slow journey, or staying at home?"
Birmingham City Council's cabinet member for children, young people and families, Councillor Les Lawrence, said the decision to close all schools in the city for a second day had been taken after conversations with the Met Office and was based on sound evidence.
"It's very treacherous under foot. I think that the safety of parents, children - not only on the routes to schools but on the untreated playgrounds - means that the decision was one that was appropriate."
He added that he had not been motivated by a fear of legal action, but was simply acting in the best interest of the 176,000 pupils and more than 10,000 staff for whom he was responsible.
In Wales about 800 schools had been closed on Thursday. Many reopened but then had to send children home early on Friday as further snow spread in.
Eventually more than 600 schools across Wales were closed.
Some parents worked from home, where the nature of their jobs permitted this.
But childcare services website Emergencychildcare.co.uk reported record demand for childminders on Thursday as parents were forced to choose between staying at home to look after their children and finding someone else to care for them.
Ben Black, the website's founder, said: "Many parents are worried that their bosses will think they are making excuses if everyone else has made it into the office."
Oxfordshire's council also predicted many schools in the county would remain shut on Friday, as it gave a warning of "widespread ice on all roads" overnight, and more than 80 did so.
Buckinghamshire's announcement said: "Due to forecasted freezing temperatures and the amount of snow still lying on secondary and unclassified roads ... it has been decided for safety reasons that there will be no home to school transport operated on Friday 9th February."
For the schools affected, it will mean an extension of next week's half-term break. In some other areas half-term is the following week.
Schools posted closure notices - with an ironic postscript from Sir Henry Floyd Grammar School: "Ski trip students will be contacted by phone during Friday morning."