Mandeep Singh pleaded guilty in the Auckland High Court to stabbing 22-year-old Parmita Rani, who died of her injuries in May this year after an exam at a school in Queen Street.
Singh also pleaded guilty to another charge of attempted murder of 22-year-old Parminder Sandhu, who was also stabbed in the neck and was taken to Auckland Hospital with serious injuries.
Singh had previously pleaded not guilty to the charges but while sobbing in the dock changed his mind, New Zealand Herald reported.
"She was very kind, she was a very friendly girl. She always took some food for me," said a classmate of Rani who had been studying IT with her.
Singh has been remanded in custody until next month for sentencing.