"Men don't like to talk about their health ... There's an expectation that opening up about their health is some sort of weakness, that they should 'take it like a man'. And as a result, we're losing many of them far too young," the letter read.
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• Local teachers grow mos for a cause
"We have to get them talking to each other, and their refusal to do so is, in many ways, more toxic than any disease.
"That's why Movember exists. For the month of November, men sport moustaches for prostate cancer, testicular cancer, mental health, suicide awareness, and other health issues affecting men. These hairy badges are a way for men to open up conversations, inspire donations and change, in their own, uniquely male, way."
The letter concluded by saying participating in Movember was an incredible opportunity to get "young men, together as one, talking about issues that are affecting their lives, and creating some real change".
"You can give them the opportunity to grow, not just a moustache, but a healthy mindset."
John Paul College principal Patrick Walsh said it was a worthy cause and students were encouraged to donate, but the school would not suspend its personal hygiene policy.
"The cause is excellent and we are fully supportive of students contributing but we would not allow students to take part at the expense of our high personal hygiene standards.
"We do require students to be cleanly shaven, though we do make allowances for students who can prove they maintain facial hair for religious reasons."
Walsh said he had not received any requests from students to take part in the fundraiser this year.
Rotorua Lakes High School principal Bruce Walker said his school had allowed students to take part in the fundraiser in the past.
"It hasn't been an issue before, but we haven't had any students asking to do it this year.
"I wouldn't be against it, but November is not the best month for students as they have their external exams and should be focusing on that, rather than preening their moustaches."
Western Heights High School said in a written statement, "at this point we have had no requests from students to support Movember so this is not an issue".
Rotorua Boys' High School did not respond to requests for comment.