"This has been a five-year process so far and we're constantly looking at refining things instead of sitting back and thinking 'it's done'."
He said the schoolwide programme included a coloured card system where a pupil got a green card that was clipped when their school day was completed without incident.
Misbehaviour earned a warning and orange, red or black cards for each successive infraction.
Pupils who were red-carded spent time in a "buddy class" of usually younger pupils and black-carded pupils were dealt with by Mr Nelson or principal Ed Hodgkinson.
At the other end of the scale green cards go in to a regular draw that offers well-behaved pupils the chance to win sought-after books.
He said there were also Golden Rules posted throughout the school, comprising maxims about honesty, diligence, obedience and kind and caring actions, and a Golden Time scheme was in place for well-behaved pupils who earned a Friday afternoon reward ranging from face-painting, cooking and meals, to mudslides.
The school withdrew misbehaving pupils from class or the playground for a set number of days and a "reflection sheet" was completed about the incident that led to their withdrawal, he said.
The school last year started a boxing and fitness scheme involving eight teacher-nominated boys who began training at the Wai Weight private gymnasium in Masterton before taking boxing lessons at the Masterton Young Citizens Club.
The pilot scheme sought to improve fitness and personal discipline among the boys, he said, and held up as role models champion Masterton bodybuilder Bevan Mackenzie and Wairarapa police Senior Constable and boxing coach, Dave Drummond.
Mr Nelson said shared goals and the unity of staff, pupils and parents were vital to the success of the programme. "I think it's working well because expectations are consistent, staff are consistent and teachers, students and to a great extent the families, are all on the same page.
"I was going weeks at a time last year without having to deal with anything and that has a huge effect on learning. I would be happy to take any parent into any class, without question, and I'm certain good things will be happening in that class.
"But the really cool thing is that just about every student gets through every single day doing the right thing."