The Male Survivors of Sexual Abuse Trust (MSSAT), a support group, urged New Zealand parents to believe their sons if their male kids complain of sexual abuse.

The advice from the support group was made on the same day that James Parker, the former deputy principal of Pamapuria School, was given by Justice Paul Health of the High Court at Whangarei on Friday a sentence of preventive detention with minimum 7 years prison term.

Mr Parker had admitted to 74 sex charges related to sleepovers with male students at his Awanui farm between 1999 and 2012.

Ken Clearwater, founder of MSSAT, pointed out that boys are less likely to report incidents of sex abuse because of shame and guilt. "They carry the belief that they may have been responsible for it ... boys don't accept that they are a victim of a crime," Mr Clearwater was quoted by TVNZ.

In the case of Mr Parker's 20 victims, to whom he admitted to the court that he was responsible for more than 300 acts of sexual abuse, one boy came forward in 2009 and told of his suffering in court.

"I told some of my own family members about it but they didn't believe me. They told me I was lying. I remember them saying 'he wouldn't do that,'" The New Zealand Herald quoted the boy.

Besides suffering from a disbelieving family, the boy was also bullied and teased by other students, lost friends and even entertained thoughts of taking his life because of the abuse he suffered in the hands of the school official.

"I blame you for a lot of my sad feelings, for my anger. I think you are sick," he told Mr Parker.

But because the boy later withdrew his claim of sex abuse, the only thing that police could do was interview Mr Parker, who denied the allegations.

But in 2012, another boy came forward and corroborated the claims of the first boy. The testimony of the second boy helped nail Mr Parker.

Explaining the disbelief of many Kiwi parents to allegations of New Zealand boys of sex abuse, Mr Clearwater pointed out, "I believe they go into a state of shock, especially if they've got their own issues, they don't want to know how to deal with it."

Unless parents listen and believe their kids, "There will be hundreds of girls and boys who were sexually violated last night while we were sleeping in the comfort of our own homes," Mr Clearwater warned.

Alan Bell, director of ECPAT Child Alert New Zealand, an anti-child sexual exploitation agency, added that chances are many of Mr Parker's victims will have their young lives changed forever while dealing with the trauma from the betrayal and sexual abuse they experienced at a young age.

"The abuse in this case was inflicted by someone who used the privileged position given to him as a teacher and he betrayed the trust and responsibilities vested in him. It was a betrayal of the worst kind," Mr Bell stressed.

The justice added, "The trust reposed in you by the community in general was breached in the most appalling fashion."