A Korean high school student accused of stabbing his teacher talked about it before the attack, then went to school with a knife, police say.

Police prosecutor Sue Newlands told the Auckland District Court yesterday that Tae Won Chung discussed attacking Avondale College teacher Dave Warren with others before Tuesday's knifing.

Ms Newlands said police opposed bail because those discussions - and the carrying of a knife to school - showed a level of premeditation.

Police were also concerned the 17-year-old could try to contact students who witnessed the attack, or attempt to flee New Zealand, she said.

Chung showed no emotion during his appearance, keeping his head down while listening to proceedings through a translator. He stood wearing a police-issue boiler suit, his hands clasped in front of him. His lawyer, Jo Scott, argued he should be granted bail as he had no previous convictions and could live with a 24-hour curfew and an order preventing him from going near Avondale College.

Ms Scott told the court Chung's homestay mother, sister and brother were in court to support him, and were very "fond" of him. His homestay mother cried quietly in the back of the court.

Ms Scott said police had no grounds to suggest Chung would interfere with witnesses, and he was not a flight risk.

Judge Christopher Field remanded Chung in custody until March 18, saying Mr Warren's views were not known because he was still in hospital and the police had not spoken to him.

A psychiatric assessment would also have to be done before Chung's next court appearance to determine if he was fit to stand trial, the judge said.

"Given the nature of the charge against him, in what are a bizarre set of circumstances, it is not a case bail should be granted at this time."

Judge Field rejected defence attempts to have Chung's name and image suppressed, saying to do so would just be "delaying the inevitable".

Outside court, Chung's homestay brother, John Park, told the Herald he had received a phone call from an upset Chung shortly after the stabbing.

He said he had picked Chung up from Avondale College on his scooter and taken him to a park "to talk about what happened".

Asked what condition Chung was in, he replied: "Stressed." He said Chung had told him he needed to go to the police and they were on their way there when they were apprehended.

Other students supporting Chung in court said he was provoked by racist comments. One said "it wasn't in his nature to do this".

Chung's father is expected to arrive in New Zealand today.