Wanganui fire station officer Shane Dudley said the lightning struck one of the back buildings at the school and also damaged concrete, where the electricity went to earth. Firefighters helped relocate children but kept them inside to protect them from the wild weather.
"Little kiddies getting cold - not great," Mr Dudley said.
Metservice's Heath Gullery said the Wanganui region had seven lightning strikes during yesterday's storm.
Taina Hiroti was driving near the intersection of Puriri St and Mosston Rd at about 1pm when the second power pole from the corner was hit by lightning.
"We saw the lightning come from the sky - it shocked the box at the top of the power pole. It was just like ba-boom boom - there was just sparks everywhere," she said.
"It was really crazy - I've never seen it before. It was hard-out raining."
Jayden McMillan was in his kitchen when he saw lightning hit the Balgownie Reserve near Tui Place in Gonville.
"I saw the lightning strike the ground, then the power went out and there was a massive bang. It shook the whole house," he said.
"I thought the window was going to smash."
He said the lightning hit about 600 to 700m away from the end of Tui Place.
Mr McMillan's "bloody coward" of a dog went and hid under the kitchen table after the strike, which happened some time between 12.55pm and 1.05pm.
Firefighters also went out to Ruapehu St in Castlecliff, where lightning hit a large tree and left a "big cut down the side", Mr Dudley said.
The tree would need to be taken down, but the job was "too big" for firefighters and would need an arborist.
Firefighters informed nearby residents of how to keep safe if the weather caused any more problems.
Metservice said there was nothing unusual about the number of strikes early yesterday afternoon. The heavy rain, thunder and lightning was expected to reduce to occasional showers by today.
Yesterday's deluge came after weeks of rain in the region. Between May 10-June 10, 175.8 millimetres of rain fell - the May average is 72mm and the June average 107mm. The total for May was 125.4mm.