Auckland Grammar First XV produced a stunning comeback to claim their first win at King's College since 2014.
King's made a fast start, holding a 24-10 lead in the first half before Grammar delivered a big finish.
Trailing 32-17 in the 46th minute, Grammar scored 17 un-answered points to snatch the win with a late penalty.
The two schools have now faced each other on 209 occasions since the first match in 1896, with Auckland Grammar triumphing 133 times, King's College notching up 60 wins, and 16 draws.