The first half points came from the boot of Rotorua first-five Jayden Savage and Hamilton first-five Orbyn Ledger who kicked a penalty a piece.
Ledger's points came three minutes after the kick-off when Rotorua were penalised for offside at the ruck. The 15-year-old had no trouble slotting the 20m kick.
In fact, the talented youngster's punting ability often got his side out of trouble. On one such occasion, while the home side were hard on attack 10m from Hamilton's line, Ledger got kicked downfield to find touch on Rotorua's 22m.
But it wasn't just Ledger's kicking troubling Rotorua - his ability to break tackles, get over the advantage line or set his backline on attack also stretched the home side.
However, Rotorua were up to the task in the first half with openside flanker Dejae Adlam and Renton Barrett tireless on defence along with fullback Corban Selwyn, who was able to shut down a number of Hamilton's scoring opportunities.
Rotorua have never been shy about using their backs to get around their opponents but Hamilton centre Levi Rinnus and second-five Mason Robinson pushed up flat on Rotorua's backline, often stopping the ball getting out to Rotorua's outside men.
It effectively meant Rotorua's midfield pairing of Kaine Lewis and Jone Lasaganibau were used as battering rams.
The only time Rotorua got on the outside of the Hamilton defence was 10 minutes into the second spell. The home side were on attack, 30m out from Hamilton's line when Savage noticed Rinnus pushing up early, the first-five floated a pass over the head of Rinnus into the waiting arms of Selwyn, the fullback passed to his winger Brendon Tauranga, who was cut down five metres short. Rotorua recycled quickly and Lasaganibau looked to have bombed a certain try when he cut back inside, with men outside him. But he managed to offload a pass to Selwyn who scored, Savage converted to take the score to 10-3.
However, two minutes later, the visitors levelled when Rotorua failed to clear a kick to touch and were caught napping by Hamilton who ran it back to within a metre of Rotorua's line. The visitors put the pressure on and blindside flanker Liam Homax charged over for Hamilton's first try which Ledger converted.
Although Rotorua had the better lineout - often turning over Hamilton's ball - it was Ledger's positional kicking which made all the difference. The youngster looked to keep Rotorua pinned inside their 22, waiting on a mistake. It came with five minutes left on the clock. The home side failed to chase up in a line from a return kick and Ledger was given space between two defenders, running the 25m to score the winning try.
"Those last few minutes I could barely stand on my own two feet to be honest. All I was thinking [running to the line] was just get it down," Ledger said.
Hamilton will play Mt Albert Grammar today, in the grand final after MAGs narrowly beat Auckland Grammar 15-6.
Rotorua Boys' High School 10 (Corban Selwyn try; Jayden Savage 1pen, 1con) Hamilton Boys' High 15 (Liam Homax, Orban Ledger tries; Orban Ledger 1pen, 1con). Halftime: 3-3
