Powerful props Josh Thom and Whare Morrell created the platform for Dunstan High School's seven-try romp over St Kevin's College on Saturday.
Dunstan won the Highlanders First XV game in Alexandra 45-9 with a dominant display in the second spell to move into fifth place in the competition.
The props gained ground with the pick and go to put pressure on the St Kevin's defence and were also dangerous on the burst.
St Kevin's gave a gutsy display in the first spell and held Dunstan to a 12-3 lead at the break.
Dunstan scored two early tries but then went off the boil for the rest of the spell.
But the second half was different, with the Dunstan forwards grabbing good set-piece ball and the backs running on to it.
The best Dunstan backs were midfield pair Jayden Laws-McKay and Sam Cant who frequently broke the advantage line.
Play was efficiently directed by halfback Tom Dougherty who scored a try and kicked five conversions.
John McGlashan captain and No 8 Nathan Hull was the hero when he dashed 80m down the touch line to score the bonus-point try when Verdon College was beaten 24-3 in Dunedin.
Openside flanker Nick Ryder was quick to the breakdown and scored a try with skilled backing up.
The McGlashan team was more mobile and its forwards won good ball while the fleet-footed backline made ground with the ball in hand.
McGlashan started strongly and scored three tries in the first 15 minutes to take control.
The inside-back combination of Braydon Pennycook and Alan Steel was tidy and wing Sam Sinclair had pace out wide.
Otago Boys' scored 12 tries when it beat South Otago 75-0, with first five-eighth Lance Taylor scoring three tries and kicking four conversions for 23 points.
Otago Boys' moved into second place in the competition behind Southland Boys', which beat King's 38-3 midweek.
King's dropped to third with Gore fourth.
In other games, Central Southland College beat Kavanagh College 13-0 and Gore beat Waitaki Boys' 25-6.
Points after nine games: Southland Boys' 41, Otago Boys' 38, King's 37, Gore 34, Dunstan 22, Waitaki Boys' 19, John McGlashan 19, Verdon 18, Kavanagh 9, Central Southland 12, South Otago 10, Kavanagh 9, St Kevin's 5.
Two King's players have been suspended following an incident in the match between King's and John McGlasham on June 19.
A disciplinary committee decided on Friday to suspend Hayden Fleury for five weeks for punching and Junior Faa'vae for two weeks.
King's has seven days to appeal the suspensions.
