"I kept it on purpose. And to be fair, it was true," he says.
Determined to turn around the results, staff set five-year goals and examined the way they engaged with classes. Students were clearly told what credits they had and how they could get to a pass or better award, and teachers gave up holiday time to offer tutoring and help.
"We had 200 boys turn up on the first day ... we made it a communal thing for the boys, we put on lunch for them. I think out of that, the boys started trusting what the school is doing for them," Mr Evans says.
Samson and his 1st XV teammates - role models for their peers - started getting a clear message: "School first."
The team, which had a 27 per cent pass rate across three NCEA levels in 2010, was made to attend homework club. Last year their pass rate had jumped to 79 per cent.
Samson, who wants to study law and is now the school's head boy, passed NCEA Level 2.
"I changed, and it was just a switch of attitude. But I'm thankful that I did," he says.
Year 12 student Zion Ioka, who passed NCEA Level 1 with excellence, said teachers had fostered competition between students in his classes.
"When I first started, everyone just kind of kept to themselves about their results. But now everyone talks about wanting to beat each other."
While there is still much work to do at NCEA Level 3 (which has a 63 per cent pass rate) and on University Entrance, the school's five-year goals were now within reach, Mr Evans says.
Kelston's NCEA Level 1 pass rate went from 58 per cent in 2010 to 81 per cent last year, with the Level 2 pass rate going from 59 to 80 per cent.
Mr Evans, the former principal of De La Salle College and who is completing a PhD on Pacific Island school achievement, said improving results is about self-belief.
Some of his students faced obstacles, but the school could not excuse itself by pointing to them.
"Talk of the 'tail' [of underachievement], particularly for Maori and Pacific Island boys, they're not silly, they pick up on it in the news and the papers. Many of the boys probably needed a belief that they were going to pass ... it's no good having all these programmes running if at the end of the day they don't believe they will pass."