Sam Mayes booted five goals for SA while Melbourne father-son prospect Jack Viney again featured in the best.
In Tuesday's other game, Vic Metro weathered an unusual second-quarter interruption to defeat Vic Country by 30 points.
The sprinkler system at Blacktown flooded the ground for 14 minutes in the second term but that didn't deter Metro's charge, with Joe Daniher booting another three goals.
Daniher, the son of Essendon and Sydney Swans stalwart Anthony, is eligible to be selected under the father-son rule by both clubs.
Darcy Bailey, the son of Melbourne coach Dean Bailey, was another familiar name among Metro's best players.
South Australia 10.15 (75) def Western Australia 7.6 (48)
Goals
SA: Sam Mayes 5, Ben Kennedy 3, Travis Schiller 1, Brodie Grundy 1
WA: Shannon Taylor 2, Dayle Garlett 1, Chris Yarran 1, Mason Shaw 1, Brant Colledge 1, Chris Deluca 1
Best
SA: Todd McKay, Josh Archer, Tom Whittlesea, Travis Schiller, Jack Viney, Brodie Grundy, Nick Amato, Joseph Sinor
WA: Riley Hutchinson, Corey Chalmers, Adam Carter, Shannon Taylor, Brant Colledge
Vic Metro 11.4 (70) def Vic Country 4.10 (40)
Goals
Vic Metro: Joe Daniher 3, Rory Atkins 2, Kristian Jaksch 2, Nick Vlastuin 2, Darcy Bailey 1, Nathan Hrovat 1
Vic Country: Jason Pongracic 2, Brad Crouch 1, Jayden Gee 1
Best
Vic Metro: Jonathan O’Rourke, Nick Vlastuin, Lachlan Plowman, Darcy Bailey, Fabian Brancatisano, Nathan Hrovat
Vic Country: Jason Pongracic, Tim Membrey, Brad Crouch, Lachie Whitfield, Dylan Weir, Oliver Wines
Round two matches to be played on Wednesday, July 7 at Bruce Purser Oval, Rouse Hill and Blacktown Olympic Park:
Bruce Purser Oval
11am: NT v NSW/ACT
12.30pm: Tas v World XVIII
Blacktown Olympic Park
6pm: QLD v South Pacific
For the latest scores, news, fixtures and profiles from the NAB AFL Under-16 Championships visit www.afl.com.au/u16s.
