The 15-year-old is understood to have fallen on Saturday night and died on Monday.
She was a pupil at Dominican College in Fortwilliam, north Belfast.
In a statement given to the BBC, the school said it was devastated by the loss of the girl, as a result of a tragic accident.
It said she was a bright, talented girl who was very popular with pupils and staff.
Pupils at the school were told of her death at a special assembly