A young girl and another person were pulled from under a collapsed school wall at Milnsbridge, near Huddersfield, after storms hit the area.
The girl was taken to Huddersfield Royal Infirmary, suffering from minor injuries, an ambulance spokesman said.
It happened as storms brought flooding and power cuts across West Yorkshire.
An ambulance service spokesman said they were called to reports of two people trapped beneath a wall at Crow Lane Junior School at 1730 BST.
"We got reports a wall had fallen on two people, possibly children, at Crow Lane Junior School.
"The ambulance crew and police pulled them free and one child went to hospital," the spokesman said.
The fire service took 500 calls between 1700 and 2000 BST on Thursday, which it says has stretched it to the limit.
Flooding is affecting areas across the county after storms brought an average month's-worth of rain in an hour.
Around 5,000 homes in Sowerby Bridge, Elland and the centre of Leeds were without electricity as engineers struggled to reconnect the power.
'Roads turned into rivers'
Paul Stevens, a former Met Office observer, lives in the area and told BBC Look North it was the worst storm he had ever seen.
Between 1715 and 1810 BST 67mm of rain fell which is the usual amount for the whole of August, he reported.
"There was constant thunder and lightning at one point and the roads have turned into rivers," he said.
Emergency services were called to the area as homes and shops were flooded.
Engineers were also out at Luddenden, near Halifax, after a warning that water from a dam downstream of Jowler Mill was threatening 50 nearby homes.
Water levels in the area fell during Thursday afternoon and the engineers managed to shore up the dam preventing the flooding threat.