Jeni Larmour was one of two 18-year-old women who died in Newcastle University student accommodation after they were thought to have taken ketamine.
The university said both were thought to have been on campus for less than 48 hours.
Separately, an 18-year-old man from nearby Washington, Tyne and Wear, who was not a student, and a 21-year-old from Northumbria University died after they were thought to have taken MDMA.
Ms Larmour had been deputy head girl at The Royal School in Co Armagh.
In a tribute on Facebook, the school said she was “a model pupil, exemplifying many of the values which this school seeks to promote”.
She was an enthusiastic pupil who joined in school activities and “was blessed with a beautiful singing voice”, it added.
“Jeni was a spirited and independently-minded girl with clear views which she was happy to articulate in a respectful manner, and she was possessed of a well-developed sense of justice.
“We have no doubt that, given her academic ability and personality, Jeni had a bright future ahead of her and we are saddened that has been so suddenly cut short.
“We extend to her many friends, her family, brother, and parents our sincerest sympathy at this tragic time and assure them of our prayers and practical support.”
Northumbria Police arrested a total of 10 people and carried out searches of student accommodation using drugs dogs.
Professor Fiona Measham, chair in criminology at Liverpool University and co-founder of The Loop – a harm reduction charity which promotes health and well-being in nightlife venues – said freshers’ week in lockdown may have played a part in the deaths.
“There’s no nightclubs, and pubs close at 10pm,” she said.
“Nightclubs are a semi-safe space, they have registered door staff and security, the bigger clubs often have paramedics, they have chill out spaces.
“If you don’t have nightclubs open, you lose that safety net.”
But Newcastle University pro-vice chancellor Professor Chris Day disagreed, saying freshers’ week had barely begun, and stressed that there are support services for new students.
“Whatever difficulties you have gone through, we have ample support both at the university and in the city,” he said.
“Whatever those problems are, please do not turn to excessive alcohol or drugs to solve them because you have seen the potential consequences.”
Chief Inspector Steve Wykes said: “Illegal drugs are never safe and the danger that they pose cannot be under-estimated.”
