They scored 884 points in their win, second-placed Francis Douglas/Sacred Heart Girls' scored 824 and Takapuna Grammar were third with 792.
Bay rivals Taradale High, who specialise in adventure racing and finished fifth at last year's national final, were fourth on 790.
Twenty-four teams competed in the North Island race, which serves as the qualifying event for the 2017 Genesis Energy Hillary Challenge Final - a five-day-long event in December held at the Tongariro Outdoor Pursuits Centre.
Will the Havelock/Napier team be going?
"Sure, we're all pretty keen. We're already talking about a replacement for Dylan," said Tidswell of captain Dylan Kirk, who was the only Year 13 student in the team of Year 11 and 12 students.
Only teams with four boys and four girls are eligible for the national final.
Carolyne Nel, Polly Cavanagh and Emily Dunn of Napier Girls' teamed up with Havelock North High's Kaiyin Hardy, Thomas Culham, Zane Shadbolt, Tidswell and Kirk.
"Dylan was really good. He kept us motivated," Tidswell said. "He pushed us. We all had to be positive and had to have a really good attitude."
The team worked as a tight unit. It helped that they knew each other from orienteering. Nel and Tidswell are current New Zealand secondary school representatives.
The Westlake Boys and Girls' team, with top orienteers in Ryan Williams and Sofie Safkova, were a threat when they started the rogaine stage more than seven minutes ahead of Havelock/Napier.
But Westlake blew that lead.
"They were smashing us in the first two stages," Tidswell said. Havelock/Napier played to their strength in the rogaine, collecting all the controls and attempting only one of the four mystery activities that could be done at the same time despite the tempting points on offer.
That strategy proved decisive as Havelock/Napier scored 600 in this section while only three other teams managed more than 500.
Francis Douglas/Sacred Heart were the closest on 538.
