The area has been sealed off by police

The fight broke out about 1000 GMT on Tuesday between two boys at the Birkbeck School and Community Arts College, North Somercotes near Louth.

Police say the boy, named locally as Luke Walmsley, was taken by air ambulance to Grimsby hospital but he died soon after.

Inspector Lee Freeman said a 15-year-old pupil had been arrested and is being questioned by Skegness police.

Police have refused to confirm the cause of death.

A Home Office pathologist was carrying out a post mortem examination on Tuesday, and the cause of death is expected to be announced on Wednesday.

The school, which has only 276 pupils, has been closed and is expected to remain closed on Wednesday.

This is a very traumatic time for both the community and those who know the victim Inspector Lee Freeman School incidents 'extremely rare'

On Tuesday, children were taken from the school in coaches or were collected by parents.

The incident is believed to have happened in a school corridor during the morning break.

Inspector Freeman said: "Chief Constable Tony Lake, who was in the division, visited the school and has spoken to the headmaster.

"He has expressed on behalf of the force and all my staff the sympathies and thoughts for the victim, his family and friends and all the pupils at the school.

"This is a very traumatic time for both the community and those who know the victim and we look forward to supporting them."

The area has been sealed off and preserved for forensic examination.

Pupils who witnessed the incident are to be interviewed by specially trained officers under the vulnerable witness scheme.

A team of counsellors have been brought in to talk to those who feel they need help.

Bouquets of flowers have been left on the lawn in front of the school.

Many in the small community have been shaken by what is seen as a totally out of character incident.

One parent said: "It was very worrying, I was worried myself.

"I thought it might be my lad until I came here and talked to the staff."

BBC correspondent Kevin Bocquet said there was "absolute shock" in the village.

"People cannot believe what has happened," he said.

Councillor Philip Dilkes, Labour's education spokesman on Lincolnshire County Council and a member of the Lincolnshire Police Authority, said: "This is a terrible tragedy. Our thoughts are with the family and friends of the dead boy."