Grammar beat fellow Auckland school Kings College 3-0 in the final of the elite tournament at Dunedin's McMillan Centre yesterday.
The traditional powerhouse first won the Rankin Cup in 1934, and has been the dominant school this decade with triumphs in 2003, 2004, 2006, 2007 and now 2009.
Nick Bint, Ben Joyce and Callum Longden scored the goals for Grammar, which led 2-0 at half-time.
Grammar's defence stifled Kings College, while Ketan Hari and Joseph Crooks were influential further forward.
Kings tried valiantly and came close to scoring on a couple of occasions, but overall Grammar was the more consistent side and held the ball better.
Hamilton Boys High School claimed third with a 1-0 win over defending champion Westlake Boys.
Otago Boys High School followed up last year's surprise second placing with sixth, beaten 2-1 by Christs College on the final day.
Both teams had penalty corners shut down in the first half and it was 0-0 at the break.
Christchurch Boys took a 1-0 lead shortly after half-time and made it 2-0 15 minutes later.
Otago Boys fought back with a series of penalty corners and eventually got a field goal from Kane Russell with five minutes on the clock.
Eight players in the Otago Boys squad are returning, so the school is well placed for a tilt at the Rankin Cup next year.
Meanwhile, St Hildas Collegiate School has been relegated from the top-tier Federation Cup but at least finished the tournament on a bright note yesterday.
St Hildas beat Christchurch Girls 4-1, with Jess Tisdall scoring a hat trick, to claim 13th place at the Wellington tournament.
