Four people have been arrested over the death
A memorial service has been held at the school attended by Ryan Quinn.
The 14-year-old died after being hit by a train on tracks near Portrush late on Friday night.
Three men and a teenager, arrested over the death, have all been released on bail.
Ronnie Kelly, the principal of St Joseph's College in Coleraine, described Ryan as an "excellent young man".
"But it's possibly best coming from the words of the children themselves - they relate him as a very cheerful and happy young man," said Mr Kelly.
It is understood police are investigating reports that Ryan was being chased just before he died.
They want to speak to anyone who witnessed a row in a local bar on Friday evening.
They believe Ryan had been in a bar near the scene of his death that evening.
A police spokesperson said detectives were "particularly keen to speak to anyone who may have witnessed a disturbance or altercation either within the bar, or anywhere outside the bar after 9pm".