The tribunal has found the principal guilty of serious misconduct, censured him, and barred him from any school leadership role until he has proved that he is "maintaining proper boundaries".
"We wish to make it clear that the respondent's conduct is not befitting of any teacher and is even less acceptable in a principal," it said.
"We accept that it is not easy for a woman on her own to deflect the unwanted advances of an intoxicated visitor late at night, and particularly when that visitor is her boss."
The principal applied for name suppression "on the basis of the interests of himself and his wife".
The tribunal agreed to suppress all names, including the name of the school, because of the principal's "ongoing mental health concerns".
He told the tribunal that he was diagnosed with type 2 bipolar disorder by neuropsychiatrist Dr Guillaume Newburn in 2008.
"After two years of trialling medication, he achieved the ideal combination in about 2010 or 2011," the tribunal said.
"In 2015, Dr Newburn trialled a reduction in medication and the events that are the subject of this charge occurred around this time.
"The [principal] said that he was not coping well and came to rely on others for support. [The female teacher] was a staff member he relied on heavily during this time."
Newburn told the tribunal that the principal was "clearly depressed" when assessed in September 2015.
"In phasing down the dose of medication, [the principal] became significantly more depressed. This was followed by a mild hypomanic state," Newburn said.
"It is likely that he was impaired as a result of his depressive phase of bipolar affective disorder. Alcohol would have made things worse."
In an agreed summary of facts, the tribunal found that the principal first visited the teacher's home some time after 8pm one night in August or September 2015 after drinking alcohol.
"They talked for a few hours about matters including the deputy principal's position," it said.
The female teacher then went to bed.
"A short time later, [principal] opened [the teacher]'s bedroom door. [The teacher] asked him what he was doing and made it clear that he would not be sleeping in her bed. The [principal] slept on the couch."
The principal tried to ring the teacher six or seven times between midnight and 1.02am on September 23, and twice at 11.58pm the next night, and then texted her just after midnight the following night saying, "Why won't you answer?" and "Please answer."
The teacher texted back the next morning saying: "I was asleep u egg."
The next day the principal texted again asking if he could "call around for a catchup".
The teacher told him not to come and said she and her mother were going to Rotorua for the weekend.
The principal texted back saying he and his wife were splitting and adding: "I was just actually looking for some company."
Ten days later the principal turned up uninvited at the teacher's house at 10.45am. She and her son pretended not to be home, and later that day she told the principal at school that he could not visit her at home.
Despite this, 12 days later the principal again knocked on her door at 2am after drinking alcohol. The teacher and her son again pretended not to be home.
The principal told the tribunal that he has since "voluntarily removed himself from the [teaching] profession", gave up alcohol, and increased consultations with his psychiatrist.
Newburn told the tribunal that the principal was depressed last year, but now displayed "excellent knowledge of his conditions, associated risks, and what he must do to maintain good health".
"In his opinion there is nothing in his current presentation that would suggest that he is other than fully fit to return to his role as a principal," the tribunal said.
But the tribunal ruled that the principal should not be allowed to return to a leadership role immediately.
"The demands of a principal require a degree of resilience and independence that the [principal] has not satisfied us of," it said.
It ordered him to have professional mentoring for two years, providing quarterly reports from the mentor and his psychiatrist, and must not take up a school leadership role until the Education Council's manager of teacher practice agrees that it is appropriate.
