Perth's elite private boys' schools have banned spectators from drinking alcohol during interschool sport fixtures or risk the match being forfeited.
The Public Schools Association has added to its code of conduct the requirement that "no alcohol to be consumed during the hours of play".
PSA president and Scotch College headmaster Alec O'Connell warned in last week's school newsletter that a breach of the new policy by parents or other spectators could come at a cost to students.
"While I know some will take exception to this policy, please understand that a breach by any school and their supporters could result in a forfeit of the result of the respective fixture where the breach of policy occurred," he wrote.
Dr O'Connell said the heads of the seven schools in the PSA decided to add the policy after "a couple of incidents" occurred last year at all-day cricket matches involving supporters who had been drinking.
"There was one game in particular last year when some responses to umpiring decisions got a bit vocal towards the end of the match," he said.
"We just didn't think that drinking alcohol during hours of play is conducive to role-modelling for boys - or role-modelling for sport in general."
The PSA includes Scotch, Wesley, Aquinas and Trinity colleges, Guildford Grammar, Christ Church Grammar and Hale School.
Dr O'Connell said he could not comment on which schools were involved in the incidents.
"It was nothing major but we felt it could become more of a problem if we allowed it to continue," he said.
The tough stance comes as the University of WA student guild moved to ban alcohol from all orientation events this week in the wake of last year's O-camp scandal involving allegations of sexual harassment and underage binge drinking.
UWA banned orientation camps and alcohol-related sponsorship in September after a damning internal review found the camps breached liquor laws by serving alcohol to drunk, underage students.
Guild president Cameron Barnes said the decision had since been made to make O-week, which begins today and ends with a music festival on Friday, alcohol free.
"We are encouraging students to get involved in a rich campus experience which has nothing to do with alcohol," he said.
He said the move had been unpopular with some students but those over 18 were welcome to drink elsewhere, including the on-campus tavern.