The home side, unbeaten this year, will meet Southland Boys' High School in the final of the Highlanders First XV competition.
Otago Boys' has been boosted by the return of openside flanker Slade McDowall.
He missed the past two games because of a shoulder injury but has been given the all-clear.
Otago Boys' coach Ryan Martin said the team had trained well this week and was looking forward to the game.
''For us it is about playing to our potential and recognising the occasion that it is a grand final and it is on our home ground,'' Martin said.
''It is about recognising we have a job to do and we turn up and do that job on the day.''
Otago Boys' has had two narrow wins over Southland Boys' this season and Martin has a lot of respect for the Invercargill side.
''They have only lost two games all season and that was to us. If we take them lightly, it will be at our peril.''
The Southland side has a strong forward pack, led by prop and captain Shaun Stodart, while its inside-back combinations of Liam Howley and Jarvis Wallace have been together for several years and are good operators.
The Southland side travelled to Dunedin yesterday.
The two schools are the only teams to win the competition since it started in 2009.
Otago Boys' has won all its interschool games this year, so should go into the game with some confidence.
Martin said it was not the fear of losing which drove the side.
''I think for the seventh formers [year 13s] we have in the team it is knowing that if they lose, then that is it.
"Their season is over and it is time to hand the jersey back. They want to keep playing, so to do that they have to play well.''
The school has produced some quality first XVs in the past few years and Martin said that was also motivation for the current team to not let standards slip.
Littlebourne would be damp for the match and Martin said the rain on Thursday had put paid to any hopes of a dry-weather track.
The home side would look to its strong front row to put its mark on the game and then use its dangerous backline to find some holes.
The winner of the match will face the winner of the Crusaders competition next Saturday to decide the South Island school to travel to the top four schools competition in Rotorua.
Top qualifier Christchurch Boys' High School will take on Nelson College in Christchurch for the title.
The match next week will be hosted by the Crusaders competition regional winner so whichever southern team wins at Littlebourne today will face a significant journey next weekend.
Highlanders First XV final
Otago Boys' v Southland Boys', Littlebourne, today, 1pm
Otago Boys: Matt Jones, Josh Buchan, Hemaua Samasoni, Sio Tomkinson (co-captain), Chris McNoe, Sam Porter, Kadin Brooks, Jamie Mowat (co-captain), Slade McDowall, Matt Heffernan, Matt McNamara, Jarrell Pattison, Sione Asi, Alex Frood, Jonah Aoina. Reserves: Kabe Calder, Liam Sharples, Isimeli Tuivaga, Ricki Jackson, Tim Hogan, Mike McKay, Mitch Kelly.
Southland Boys': Jack Lewis, Shawn Henderson, Blake Ryder, Pedro Bezanilla-Corte, George Karamaena, Jarvis Wallace, Liam Howley, Sumela Tavui, Sam de Vries, James Napier, Jack Capil, Ben Fotheringham, Weijo Rapana-King, Thomas Flynn, Shaun Stodart (captain). Reserves: Siuta Afa, Dom Vercoe-Bradley, Sam Calder, Logan Jones, Tim Yaxley, Mitchell Taylor, Tyler Hopa.
Referee: Adam Morrison
