Just Standfast had pleaded guilty to several charges of sexual offending against 15 girls, aged between 7 and 16 in May.
The 73-year-old also admitted five charges of assault with blunt weapons against five boys and a man.
Judge Quentin Hix handed the sentence down in the Greymouth District Court on Friday.
Upon arriving at court for the hearing, Standfast, who is now a wheelchair user, said he was "sorry" when asked questions by media.
Standfast was previously sentenced to six months' community detention and two years' intensive supervision in 2019 for indecently touching and kissing a 9-year-old student in 2012.
Former school principal at Gloriavale, Faithful Pilgrim, claimed Standfast was of "good character and fit to be a teacher" on an application form to renew his practising certificate in 2012 - months after he was told about the assault - and again in 2016.
Pilgrim was suspended from teaching for three months by the New Zealand Teachers Disciplinary Tribunal for serious misconduct and cannot work as a principal for three years.
More to come...
