During an investigation by the school, the girl said the relationship started after she asked the teacher to be friends with her on the social network work site Facebook.
They shared intimate and personal information, she said.
The relationship grew during 2012 and became physical after the teacher asked the student to play the guitar at an event, during which, she drank alcohol.
At first the teacher denied there was a physical relationship but agreed it was inappropriate. But during the tribunal's hearing, the teacher admitted the relationship was intimate.
"The respondent has accepted that he has caused [the student] distress and harm including emotional, social and academic harm," the tribunal's report said.
The teacher was censured for serious misconduct, his teaching registration was cancelled and he was fined $2012.65.
In a second tribunal decision, a teacher has been censured, but maintained her registration following a fraud conviction.
The teacher, who was not named in the decision, was convicted in March 2010, on three charges of taking, obtaining or using a document for pecuniary advantage.
Court documents said the 48-year-old was a fulltime carer of a disabled person at the time of the offending. There were three other support carers as well.
The woman submitted documents that claimed $8642 from the Ministry of Health for the support workers providing care, when they did not work those hours, and kept the funds herself.
The tribunal said the woman had an unblemished record, had been co-operative with the investigation and had repaid the stolen money.
"This is a case in which we have been forced to give serious consideration to whether we can discharge our responsibilities without deregistering the respondent.
"By a very fine margin, we have concluded that we can."
The teacher was censured and her registration papers were annotated so future employers would be aware of her convictions.
A spokesman for the Teachers Council said he was not aware of a police investigation into the case.
A complaint about the teacher's behaviour would have to come from the school, the student or her parents, he added.