Jermaine (17), a year 12 pupil at Otago Boys' High School, is the son of former All Black and Otago prop Joe McDonnell.
Like his father, Jermaine plays in the front row - the tighthead prop for the school's First XV.
Jermaine is in his first year in the top side, but it has not taken long for him to make an impact.
First XV coach Ryan Martin said Jermaine was one of the unsung heroes of the side.
"He is a bit of a dark horse, as a lot of talk goes on about our backs. But he is extremely strong and will be a key player for us next year," Martin said.
"He is extremely strong and is one of the best tighthead props going round in the competition."
Jermaine himself started off playing rugby in the centres.
But as he got "chubbier and slower" - he says - he drifted towards the front row and has been there for the past few years.
It is a position he likes and the scrum is still important in schoolboy rugby.
The side won all its games this season, picking up the South Island Supremacy Shield, and plays Christchurch Boys' in the South Island final this Saturday.
Otago Boys' won the interschool encounter 22-19 earlier in the season and Jermaine expects another hard battle.
"They were pretty tough up there and we had to be on our game. It was always going to be hard on their ground, with all their supporters."
Otago Boys, though, should not lack for confidence.
Jermaine said the team, fresh from beating Waitaki Boys' 41-3 in the final of the Highlanders First XV competition, was having a great year because of the hard work it had put in.
"Our fitness is really good, and the guys have been playing really well."
He grew up in Cromwell, where he started playing rugby, and moved to Dunedin when he began boarding at Otago Boys' High School in year 9.
His father, Joe, had spent the twilight of his playing career in the northern hemisphere, after playing eight tests for the All Blacks in 2002, and playing for the Highlanders and Hurricanes.
"He was in England playing and then in Spain, where he was a player-coach. Now, he's in Italy just coaching."
Jermaine said his father did not offer him much advice about what to do on the rugby paddock but he appears to be doing just fine without his teaching.
His mother, Camille Ainsley, was a big influence on his rugby development as was a coach in Cromwell, Paul Barling.
But it will not be Cromwell where he will be heading home in the holidays. His mother and her partner have recently moved to Perth, so he is heading there next school holidays, to meet up with family, on his first trip to Western Australia.
Until then, he will be concentrating on rugby duties and aiming to go all the way with his school side.
