In the other close-fought semi-final, South Island champions St Andrew’s won the physical battle up front and beat Hurricanes champions St Patrick’s Silverstream 24-17 after leading 14-12 at halftime.
Meanwhile, Tauranga led Westlake 19-17 at halftime thanks largely to a solo stoppage-time try under the posts by second five-eighths Cohen Satui, who jinked a good 20m to score.
It didn’t look to be enough in the face of a ferocious wind but Tauranga played brilliantly in the second spell, keeping the ball in hand, and were rewarded with tries to openside Zac Simeon and prop Jonty Bidois, while also defending staunchly.
Earlier, hooker Matt Bell burrowed over from a lineout and lock Seremaia Salikikoro also scored to give Tauranga a 12-0 lead.
Westlake hit back through left wing Flynn Holbrook and Matt Fleming – perhaps the Swans’ best on the day – while prop Demetrius Sanft briefly gave them a 17-12 lead.
St Andrew’s outscored St Pat’s four tries to three and in the second spell largely controlled play despite playing into the wind.
Looking to the girls final, defending champions Manukura are still on target to win the Hine Pounamu National Top Four Secondary Schools girls title for a fifth consecutive year after they held on to beat competitive Christchurch Girls’ High 19-14 in their semi-final.
They will face last year’s beaten finalists, Hamilton Girls’ High, who accounted for Epsom Girls Grammar 29-10 in their semi.