Aaron Davidson and Neil McFerran, both 18, were found dead in the flat in the idyllic town of Castlerock in the North after relatives raised the alarm.
They had travelled to the beach-front getaway from their homes in Newtownabbey, on the outskirts of Belfast, to relax and have fun before turning their minds to future plans when their exam grades were published.
Another teenage friend, Matthew Gaw, who was unconscious when emergency services broke into the flat in the Tunnel Brae Court complex, was revived and was being treated at the Causeway hospital in nearby Coleraine.
It is believed all three were overcome by carbon monoxide fumes.
The headmaster of the teenager’s school, Glengormley High, said they were role models for fellow pupils.
“Both boys had displayed exceptional talents in their time here and were popular and valued by both students and staff,” said principal Lex Hayes.
“Aaron and Neil were both prefects and acted as role models for younger pupils. They will be sadly missed by all who knew them in school.”
The other seven apartments in the complex were evacuated after the incident and the building remained cordoned off as the police and officials from the Health and Safety Executive examined the scene and checked all the gas appliances.
Mr McFerran was a talented actor who was also an active member of the school choir. He had just completed his AS level exams after transferring to Glengormley from nearby Monkstown Community School after his GCSEs.
Mr Davidson attained some of the school’s best ever marks in his GCSE exams two years ago and was planning to go to university.
Mr Hayes said counselling would be provided for all pupils in the school to help them overcome the grief.
“Although I have only been at Glengormley High School for two years, I knew both pupils well, and they were great boys, and we were very proud of both of them,” he added.
Andy Conn, the French teacher at Monkstown Community School, said Mr McFerran’s death had left the school “stunned”.
“He was an all-round nice guy. He was really into his drama; he was in most school plays. He would have been up on the stage larger than life. The stage was his great talent,” he said. “I would have guessed he would have gotten good A-level results and then the world is his stage. You don’t expect to have this sort of thing happen over the summer holiday; we cannot take this in. We are so sad and extend all the sympathy in the world to the family and friends and our ex-pupils.”
The teacher said the teenager had returned to the school after leaving to work with the youth club.
Mr Davidson was from Fernagh Road in Newtownabbey and Mr McFerran was from the Kings Walk area of the town.
Ulster Unionist Assembly member David McClarty warned of the deadly consequences of carbon monoxide exposure.
“This tragedy necessitates a full and thorough investigation. Carbon monoxide poisoning is often considered a ‘silent killer’ — being odourless, colourless, tasteless — and as such we need to ensure that people protect themselves adequately.”