A total of 49 per cent of Girl's College students voted for National, while 20 per cent voted for the Greens, followed by Labour.
Mr Key talked about New Zealand today being the best it has been in a long time for young people.
People were living in a highly competitive, multicultural society in exciting times and the future was bright, Mr Key said.
"The best years are still ahead of New Zealand because of a massive explosion of middle income wealth in Asia. It's going to create the biggest transformation of wealth in the region and obviously New Zealand is set to reap the benefits from this."
Mr Key also talked about his own background, his solo mother raising him while living a state house and his determination to become Prime Minister.