An 11-year-old girl was rushed to hospital after falling from a balcony at a comprehensive school.
Parents said some pupils were sent home following the incident during breaktime at Caldicot School in Monmouthshire, South Wales.
It is thought to have been witnessed by many pupils.
Gwent Police said in a statement: “We received a report from Mill Lane, Caldicot, at around 12.15pm on Monday, December 13, that an 11-year-old girl had fallen from a balcony."
The school, which opened in 2017, has several balconies overlooking open internal courtyard areas, reports Wales Online.
It was built at a cost of £36.5million and has 1.300 pupils.
A Monmouthshire County Council spokesman said on Monday: "Following a serious incident at Caldicot Comprehensive School this morning we are supporting learners and their families along with the wider school family.
"We are working closely with all relevant agencies."
A Welsh Ambulance Service spokesperson said: "We were called at approximately 11.20am today, Monday 13 December, to reports of a person having suffered a fall from height at Caldicot Comprehensive School.
"We responded with one rapid response vehicle and one emergency ambulance. One patient was taken to University Hospital Wales, Cardiff for further treatment."
