Further snow and icy conditions is set to close schools on Thursday
A teaching union has said it fully supports the decision by nearly 550 schools across Wales to close following severe weather conditions.
The NUT Cymru said heavy overnight snow left schools with "little choice".
Parents now have to wait to find out if they will be facing a third day of mass school closures.
At least one county has withdrawn home to school transport for Wednesday because of continued forecasts of adverse weather conditions.
Rhondda Cynon Taf said the decision on whether to open schools on Wednesday would rest with individual heads.
By 1830 on Tuesday, 15 schools in the county borough had already signalled their intention to close the next day.
The Met Office has issued a severe weather warning for icy roads later on Tuesday, and forecasters have said more snowfalls are possible from Wednesday night.
NUT Cymru secretary David Evans said: "The decision to close a school is never one that can be taken lightly.
"The severe weather warnings received and the heavy overnight snow meant that head teachers and other school leaders had little choice when it came to deciding if they should open.
"It is to the credit of those involved that they chose to make the decisions early so that alternative arrangements could be made."
He said heads had to assess the risks to staff and the hundreds of pupils who may be coming to or from non-gritted areas and had to "err on the side of caution".
He added: "When you factor in difficulties related to travel arrangements, especially in those schools that have a wide catchment area, there is usually only one outcome."
Mother-of-four Dr Jo Longstaff, who owns four private general practice clinics in Cardiff, said she understood the decision taken to close her children's primary school.
"I heard quite late on in the morning and on a selfish level it would have been nicer to have known earlier," she said.
"I understand the situation. The buses [taking the children to school] come from the Rhondda and they would have had difficulty getting the buses here, and there was more snow forecast later on in the day."
Her children had to attend surgery with her for two hours, but later went to build snowmen in a local park.
If there are further closures later this week, she intends to get together with other parents and take it in turns to look after their children.
Chris Howard, vice president of the National Association of Head Teachers and head of Lewis School, Pengam, Caerphilly, said no head would take the decision to close a school lightly.
"You have to think long and hard because you'll probably never win. There is a sense of damned if you do and damned if you don't," he told BBC Wales.
In his experience, while some parents understood the decision to close, some were annoyed about having their own working arrangements disrupted.
Conversely, if the school remained opened, parents could worry about how children would get home if the weather remained bad or got worse through the day, he said.
A Welsh Local Government Association spokesman said: "The primary concern is for children's safety.
"Head teachers are best placed to take the local circumstances into account, and it is their decision."
The Welsh assembly government's education spokesman said the government was not in a position to comment on the level of school closures, adding it was the head teacher's or local authority's decision.