The family of James Magowan, the Londonderry teenager who collapsed and died in front of his school friends, today spoke of their "special wee boy" .
And the headmaster at Lisneal College, where James died, said he was a " popular" student who "embraced every opportunity" despite living with a heart condition all his young life.
His shocked friends, who watched as he collapsed and died yesterday, were today told that counselling is available at the school if they need it.
James (15), from Eglinton, was about to board a bus taking him from sports pitches at the Drumahoe campus of Lisneal College to the main building at Crescent Link, when he dropped to the ground at around 4.30pm yesterday.
Despite the best efforts of a teacher and paramedics, he could not be revived.
While a PE lesson was taking place just before he collapsed, it is thought that because of his condition, James was not fully taking part in activities.
The family were today devastated at their Eglinton home, but an uncle, who asked not to be named, paid a poignant tribute to James on behalf of the grieving family.
"James was a very special wee boy," he said.
"He was so nice to everyone. He enjoyed his school, he had so many friends and he let nothing in life hold him back."
David Funston, headmaster of Lisneal College, also paid tribute to the teenager.
He said that friends and those who witnessed his collapse would receive counselling if needed to help them cope with the tragedy.
There was also a special assembly at the school this morning.
"James had a particular syndrome which he refused to allow to get in his way," he said.
"He did not allow a disability to hold him back and he entered into every opportunity that life gave him.
"While we were always conscious to make sure we monitored everything that he took part in, he embraced everything and never complained.
"He took part in everything he could, outside class, including Scripture Union and form trips and he was a very popular young lad who was in his GCSE year.
"All our thoughts are with his family and friends at this very sad time and as a school we are trying to come to terms with what has happened."
Mr Funston added: "We have access to a counsellor through the Western Education and Library Board, and they will be available to all pupils, particularly James' friends and those who were there when this tragedy unfolded."
A former pupil of Lisnagelvin Primary School, it is expected that James' funeral will take place from Faughanvale Presbyterian Church.
Reverend Lindsay Blair said that local people were in shock at the death.
"It is a terrible thing to happen to people so young," he said.
"People in the local community can't believe it - there is a real sense of shock that this has happened."
A post mortem examination was due to be carried out on James' body to determine the cause of death.
A PSNI spokeswoman confirmed they had been informed of the death at 4.23pm.
James' death brings to three the number of Ulster children to unexpectedly die during September.
Earlier this month Patrick Devlin (13), from Ardboe, collapsed during training with the O'Donovan Rossa club.
Patrick Breen (10) also died during a GAA training session at Drumquin.