Stuart Maxwell, headteacher of Eastwood High School, said the entire school community is in shock and profoundly saddened at the tragic loss of Elliot Peacock.
The teenager died in a swimming accident on a gorge-scrambling trip at the Lillaz Falls, in the Gran Paradiso National Park in Italy on Sunday.
The schoolboy, from the Eastwood District Scouts in Newton Mearns, was on holiday with a team of leaders and friends from the group when the accident happened.
Mr Maxwell said: "Elliot was a genuinely lovely boy, well-liked and well-mannered. He would always say hello when he met you around the school. Everyone knew him as a very nice, polite, quiet lad.
"He did well in all his subjects, particularly in physics, enjoyed PE and played guitar, and he had a wide circle of friends."
He added: "We have been deeply moved to see so many of Elliot's friends and pupils from the wider school community arrive at the school to lay flowers and leave cards in tribute to him.
"There will be the opportunity for pupils and staff to sign a book of condolence at the start of term and record their memories of Elliot.
"We were privileged to have known Elliot for the three years he was with us at Eastwood. He will be very sadly missed by everyone here and all our thoughts and prayers are with his family at this extremely sad time."