Te Wharekura o Mauao lost influential rep players in first-five Tatai Proctor and centre Te Aparua Tata at halftime through injury which had a major effect on the second half performance.
Flanker Taituha Waller scored early in the half after another strong break from second-five Kiripa Clark to put Te Wharekura o Mauao up 19-3 but the game then turned Western Heights way.
Outstanding fullback Brodie Wood ran 60 metres to score and when Preston dived over a minute later it was 19-18 and the tension throughout the good sized crowd was palpable.
To their credit Te Wharekura o Mauao took control over the final minutes to hold on and record the biggest sporting crown for the school that opened in 2012.
" We set out with a particular game plan we have been playing all year and nothing much went wrong for us in the first half," Te Wharekura o Mauao coach Heywood Kuka said.
"The second half just showed how big our hearts were. Some of the younger fellahs had to step up and they did to bring the game home.
"This is five years in the making. It is important for our school. We are a Maori medium school with 180 students but it shows when you put a lot of belief into our young Maori boys they can produce anything really.
"I am so proud of them."
Tauranga Girls' scored five tries to beat Rotorua Girls', with Rose Togatogarua and Piatarihingamare Devon scoring two and Jade Tuilaepa one.
Coach Jeff Robb says he knew we had the potential to win the Bay competition.
"This is our second year pretty much together with a few sevens players who committed to fifteens and it strengthened up our team.
"Next week we go to play Hamilton Girls' for the Top Four qualifier and we have a good shot at that. We played them previously this year and we beat them 36-34 so we do have a shot."
Te Wharekura o Mauao will play the top Counties Manukau side next weekend for a chance to contest the Top Four co-ed schools title.
