Seven children were injured after a ceiling collapsed during assembly at their prep school.
Pupils at the Gems Hampshire School in Chelsea, west London, were taken to hospital with minor injuries.
A school spokesman said that a piece of plaster believed to measure around 20 sq metres fell from the ceiling of their main hall.
London Ambulance Service said that 15 children were checked for injuries and seven had to be taken to a nearby hospital.
More than half a dozen had to be treated for injuries, including dust in their eyes and bruises.
The GEMS Hampshire School is a mixed-sex private day school for children aged three to 13. Fees are £15,000 a year.
It is believed that a large section of plaster fell from the ceiling in the hall of the school that was founded in 1928.
A spokesman said: "This morning sections of plaster fell from the ceiling of the school hall at the GEMS Hampshire school in Chelsea. "The school was immediately evacuated and the emergency services were contacted. Seven children were taken to the Chelsea and Westminster Hospital with minor injuries and all have been discharged.
"Their parents were informed immediately, and all parents at the school were also contacted.
"Before children were allowed back into the school the London Fire Brigade and the district surveyor from the Royal Borough of Kensington and Chelsea independently verified that pupils were safe to return to classrooms.
"A safety assessment is currently being conducted to determine the causes of this incident. The parts of the building affected have been cordoned off.
"Our priority is the welfare of the pupils that have been affected and we will do everything possible to support them."
A spokesman for the Royal Borough of Kensington and Chelsea Council said: "Council officers will be visiting the site to assist, as appropriate, in any investigation into why this ceiling collapsed."
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