More than 80 kids came to school to find classes were called off for the day due to a number of safety concerns.

"It's just too dangerous for the kids to be here," Mittagong Public School principal Jan Morrison said.

"We only had minimum supervision at the school because we had no power, no heating, no phone connection and a lot of dangerous trees lying around on the ground.

"We thought it would be better off for parents to keep the kids at home and under the warm blankets."

Ms Morrison said the school grounds suffered extensive damage.

" I'm not sure how much damage there is, there could be $6000 to $7000 worth but we'll have to wait and see," she said.

"We had all the big trees near the demountables fall down, and they just missed the buildings, which is lucky for us.

"There were also trees that fell down onto the basketball courts, and have broken the basketball rings."

Normal classes resumed on Tuesday.

Glenquarry Primary School was all but deserted on Monday after the parents of its 38 pupils were invited by principal Denis Orman to keep their children at home.

Most boys and girls arrived at the isolated Tourist Road school in the morning as normal, with their mums or dads, but due to the widespread blackout none stayed for lessons.

"They came and went again. We stood outside and asked each parent whether or not they wanted their child to attend or go home - and they all took them home in the interest of the children's safety," explained Mr Orman, who remained at the school.

"There was no telephone and no power, which mean no heating and no toilets because they operate on pressure pumps."