John McGlashan College's Harrison Morton runs the ball up against Southland Boys' High School at the McGlashan field. Photo: Peter McIntosh
They held on to beat John McGlashan College 17-15 in a Premiership match in Dunedin.
The home side scored late but missed a crucial conversion which would have tied the score.
Otago Boys' beat Mt Aspiring College 28-0, while pre-tournament favourites King's dispatched Dunstan 73-7.
In the Championship, Otago Boys' 2nds edged South Otago 17-15, St Kevin's beat Wakatipu 22-7 and Waitaki Boys' was too good for the Otago Combined, winning 43-7.