An 11-year-old boy was killed and three other children were injured when a tree bough fell on them during a school activity holiday at a country house.
Ambulance crews were called to Felbrigg Hall, a 17th Century stately home owned by the National Trust, near Cromer in Norfolk, on Tuesday afternoon.
Three of the children were taken to hospital with back and leg injuries.
The youngsters were among 50 pupils from Heathlands Primary School in West Bergholt, near Colchester in Essex.
Head teacher John Watts described the youngster who died as a "fantastic little boy".
"We are devastated," he said. "Our thoughts and prayers are with the families of the little boy who died and the two boys and girl injured."
Two of the other children were said to be in a "comfortable" condition at the Norfolk and Norwich University Hospital. Another was described as "more serious".
Two of the injured children were trapped under the tree bough and they have all suffered crush-related injuries.
Police officers are trying to establish if weather or high winds were a factor.
A Norfolk Police spokesman said officers had been at the scene and were carrying out an investigation.
"It has been windy but we have not had widespread reports of trees falling."
The spokesman said the remaining children on the trip had been returned to their homes in Colchester.
Essex County Council said plans were being put into place to provide pupils with all the support they needed.
"There is a great deal of shock among everyone at the authority," said Tracey Chapman, the councillor responsible for schools at the authority.
"Our thoughts are with the families of the little boy who died and the children who have been hurt.
"Every support will be offered to the school and the children."