Holy Spirit College added the national crown to the state title when they won the under-15s Australian Schools Basketball Championship in Victoria.
After winning the NSW title earlier in the year, Holy Spirit battled through the early rounds of the Australian championships before beating host side St Joseph's Knox in their semi-final and Sydney Boys' High in the final.
The victory clinched the Bellambi-based Holy Spirit a second national basketball title in three years.
The team was ably led by Lachlan Dent, who had 25 points in the final, with solid contributions from fellow Illawarra guards Kyle Zunic and Mitchell Searle.
Coaches Simon Dent and Mick Cranney were elated with the boys' efforts.
"We struggled early in the week but really executed well when we had to," Cranney said.
"This is a very talented team and they have beaten all-comers this year.
"They work hard on their game, so it is great to see them rewarded with such a fantastic result."
The triumph completed an outstanding year for Holy Spirit basketballers, who won the junior, intermediate and senior crowns at the Catholic Schools NSW titles.