Former principal Uenuku Fairhall slept naked in the same bed as a student, engaged in sexualised talk with students and was partially clothed in front of students.
His actions have been described by the Teaching Council's Disciplinary Tribunal Council as "despicable" and met the test for serious misconduct.
His teaching registration has been cancelled and he has been censured.
The tribunal has today released its decision relating to an investigation into Fairhall's conduct during the school's trip to Mexico in 2017.
The decision said Fairhall breached professional boundaries during Te Kura Kaupapa Māori o Te Koutu's school trip, including sleeping in the same bed as a student while naked, sexualised talk, being partially clothed in front of students and entering a bathroom and washing the back of a student.
The trip was supposed to last 12 weeks but they came back five weeks early as a result of the allegations.
The decision is dated November 12, 2018, but its release was delayed after Fairhall tried to get name suppression, which was declined in June this year.
The decision said Fairhall accepted the incidents occurred but disputed the context or extent of the incidents.
The tribunal found Fairhall slept in the same bed as one student on multiple occasions and was naked on at least two of those occasions, slept in the same bed as a second student and entered the bathroom area when it was being used by a third student and told him to remove his underwear and washed his back and swept his hands away from covering his bottom.
He was also found to have engaged in sexualised talk to a group of students and was partially clothed in front of students.
Specifically the decision said students were asked to share beds to effectively manage costs.
After four nights of sharing a bed with a student, Fairhall took his pants off. Fairhall said he didn't wear pyjamas at home and found them too hot and restrictive. He said he was getting very little sleep and was getting run down so removed his underwear discreetly in bed so he could get to sleep. He said he wasn't aware the student knew he did it.
Later, while the students were teasing the student for sleeping with the naked principal, Fairhall joked that the student put his leg over the top of his genitals in his sleep and he had an erection at the time.
Later the student told Fairhall he didn't want to sleep in the same bed as him if he was naked and Fairhall grabbed a towel and put it around him.
The student said on one occasion he felt Fairhall's bare bottom against him, but that was the only time he felt him touch him.
The students were not allowed phones on the trip but the student eventually told his mother via Facebook Messenger.
In response, Fairhall told the investigation: "I fully realise now that it was foolish and inconsiderate to not wear clothing in the bed. But I never touched (the student) inappropriately and always tried to avoid his movements around the bed or shake him if I was awake so he would return to his side."
The decision said Fairhall scrubbed the back of another student in a shower as he had a tick on his back.
Fairhall asked the student to take off his underwear, which the student said made him feel "funny and weird".
The student covered his bottom with his hands but Fairhall pushed his hands away.
Fairhall told the student he would wash his back again the next day. The student said he could do it but Fairhall insisted saying he couldn't reach the middle of his back.
In response, Fairhall said the student developed a tick in a vein on his neck as well as a bright sore on and above his lip that looked like it could become a large cold sore and he was worried about pustules on his chest and back.
He said he told the student to remove his underwear to wash himself completely so they could be ready for the next day.
Fairhall stressed there was "no inappropriate touching or ogling".
The tribunal found insufficient evidence to support two other allegations in relation to the same trip.
On February 23, the school's board chairwoman Ruiha Ruwhiu was called by a parent to meet with them regarding a serious concern, which related to the showering incident.
The decision said Ruwhiu sought advice, contacted the acting principal, informed Fairhall of the concerns and outlined the directives to be taken by him.
These included no sharing of beds with any staff.
She drafted a travel safety policy and procedures due to the nature of the concerns. Fairhall confirmed the procedures were in place.
On March 13, Ruwhiu emailed Fairhall to say they had received a verbal complaint from two parents on the trip. The parents had requested reassurances that the students' safety was not at risk.
Ruwhiu convened an urgent board hui and it resolved to inform Fairhall that complaints relating to sharing a bed with a student, sleeping naked and no privacy in bathing had been received and sought assurances it wouldn't continue.
On March 14 Fairhall provided reassurances and instructed the school to commence an investigation and seek incident reports.
That day, the board was advised a parent had contacted police.
On March 15 police contacted the Ministry of Education and a formal investigation began. The board later decided to cancel the remaining trip and recall the students to New Zealand.
In early April 2017, following their return from Mexico, interviews were conducted with 15 students by police and social workers as part of the police investigation into the allegations.
The decision said police tried to contact Fairhall on numerous occasions and when he was spoken to, he declined to be interviewed.
The police investigation was concluded without any charges being laid.
The council's Complaints Assessment Committee submitted Fairhall's conduct met the test for serious misconduct and his inability to understand the need for, and maintain, professional boundaries with his students on the school trip reflected adversely on his fitness to be a teacher.
The committee argued Fairhall's conduct adversely affected the emotional wellbeing of all the students involved.
The committee submitted that cancellation of the respondent's practising certificate was necessary in this case to ensure public protection, deterrence and the maintenance of professional standards.
Fairhall agreed with the submissions of the committee but noted that his conduct should be viewed in light of his sleep deprivation.
The tribunal described Fairhall's behaviour as "despicable" and found that cancellation was the only appropriate penalty.
They also imposed a censure and required Fairhall to contribute to the committee's and tribunal's costs.
Fairhall resigned as principal of Te Kura Kaupapa Māori o Te Koutu in April 2017 following allegations made about his professional conduct while on the school trip. He had been principal at the school since 1998.
In a written statement at the time to the Rotorua Daily Post, Board of Trustees chairwoman Ruiha Ruwhiu said the board had accepted Fairhall's resignation with regret.
"The employment investigation has ceased as Fairhall has tendered his resignation, effective immediately, in order to pursue other opportunities.
"We would like to acknowledge that Uenuku Fairhall has made a significant lifetime contribution to our kura, our students and our community, and to Māori education."
At the time of his resignation, Fairhall told the Rotorua Daily Post he resigned "for the good of the kura" and it would allow it to move forward.
"I've enjoyed my years at the kura and I am grateful for the people I've worked with ... Up until recently it has been a positive experience and I wish the kura all the best."
The trip to Mexico, involving 21 students and three teachers, including Fairhall, was meant to last 12 weeks but was cut short by five weeks.
The three-yearly trip, which sees students billeted with Mexican families to ensure immersion in the Spanish language, has become a part of the school's culture.