The game was almost a complete mess in the first half as both teams struggled for any sort of continuity.
The young Australians also had to play a man short for 20 minutes when centre Xavier Reubens was given a red card for taking a man out in the air.
It was 3-3 at halftime, but turned into a completely different game in the second half.
The New Zealand schoolboys lifted the tempo and got some real impact off the bench, and the pace was far too hot for the Australians to handle.
Mathis inspired his troops with a follow-me performance straight out of the Richie McCaw handbook.
He went hunting for the ball, made metres at will and showed some lovely skill as he dished passes and offloads to the ball-runners on his shoulder.
He scored the best of the New Zealanders’ four tries in the second half when, after a flowing movement down the left-hand side, he produced a spin move and a nice finish.
Mathis is completing his time at Hamilton Boys’ High School but, sadly, is bound for the Crusaders, where he will no doubt became an All Black within a few years.
Other New Zealanders to impress were silky first five and ace goal-kicker Rico Simpson (Sacred Heart College), powerful hooker Manumaua Letiu (Christchurch Boys’ High School) and lock Aisake Vakasiuola (Tauranga Boys’ College).
King’s High School halfback Dylan Pledger was tidy behind the scrum, but there were not many opportunities for Southland Boys’ High School winger Kiseki Fifita to impress.
The best of the Australians was outstanding prop Will Goddard.
The teams meet again in Canberra on Monday.
