At least 20 schools in south Wales were shut by their local authority on Thursday as school buses ran out of fuel.
Rhondda Cynon Taffcouncil was forced to close 18 of its 19 secondary schools because of worries that staff would not be able to get to school.
Council leader Pauline Jarman said: "Some of our teachers won't be able to get to school through no fault of their own and that could create safety problems if there was only a handful of teachers to look after the pupils.
"Also we did not want pupils to be abandoned by the roadside if people run out of petrol."
A spokesman for the National Union of Teachers added that at least one secondary school in Powys, and a number of rural schools elsewhere in Wales, were also having to close.
Somerset County Council was expecting many of its schools to be closed on Friday as rural areas felt the brunt of the blockades.
In Basildon, Essex, 44 pupils of De La Salle school had to stay at home on Tuesday because their bus service had been cancelled. Elsewhere in the county three out of four residentialspecial schools were closed on Wednesday.
In Liverpool, the city council offered to reimburse parents forced to take their children to school by taxi.
Graham Hellier, chairman of Teaching Personnel, one of the country's biggest supply agencies, said 100 of its 1,500 teachers had phoned to say they could not make it to class on Wednesday. Schools were also having to cancel staff training because they could not be sure of supply cover, he added.
The headteachers' unions were advising their members to treat the crisis as if the country were in the grip of bad weather, with staff advised to turn up to teach at their nearest school if they could not make it in to work.
Fears that teachers' pay might be docked if they failed to show for work appeared not to have been realised in most areas.
A spokesman for the Secondary Heads Association said: "If teachers have made a reasonable attempt to get in to work, I can't see that any employer would reduce their pay."
A school in Derby was used as a refuge fpr people in Normanton were evacuated from their homes. A taxi driver had been stockpiling 200 litres of petrol in a beer barrel and wheelie bin and had caused a fire risk.