"Any incident of this nature is a major disappointment," he told the Herald on Sunday.
"We've got, in Auckland alone, 21,000 players out there having a good experience and it's so frustrating to have these isolated incidents.
"In some respects, I'm pleased it's getting highlighted because there is an issue out there in sport generally and I think we need to address it. We can't carry on like this."
Dalton said about 800 matches were played in the Auckland region yesterday. "But this one incident is putting a blight over the day's enjoyment for everyone."
Auckland Rugby staff would meet representatives from both schools tomorrow to establish whether anyone would be cited or charged over the brawl.
"The clubs, the schools, the parents and the players all need to play a part in this and all the codes are working hard," Dalton said.
"We all need to address it. It's a societal problem that we've got."
Dalton said it was too soon to say whether the ARU would launch a potential task force to investigate sideline violence.
But he added: "There is a lot of work that New Zealand Rugby and other codes are doing to address this side-line behaviour. I think we're all concerned about it."
An eye-witness to the scenes at the Otahuhu Rugby Ground yesterday told Tony Veitch's Newstalk ZB show: "It's just shocking, watching everything unfold.
"A referee got between everyone and stopped it, and sent everyone off to their sides. Otahuhu went to their side, Tangaroa went to their side.
"From what I understand somebody from the Otahuhu side went over to Tangaroa and they all started fighting, and then all these students and parents also getting involved as well, hitting students with umbrellas. It was complete chaos."
Police and ambulance staff rushed the scene as teens and spectators, including parents of some of the players, traded blows.
The injured teen was taken to Middlemore Hospital with head injuries. His condition was initially listed as serious but he was last night in a moderate condition.
Another eye-witness, Valelua Nouata, said: "It was disgusting because it was a whole bunch of adults just fighting. It was havoc. It was pathetic."
Nouata said at one stage the wild brawl continued around the fallen teenager.
"That kid had been lying there for so long. I spotted the crowd around him as the fight was still going," she said.
"Then they had another brawl, and that was the last fight that happened. That broke up, then everyone went back to that student who was just lying there.
"He was out cold."
Police last night said they were "following strong lines of inquiry" as they sought to identify the person who assaulted the 15-year-old.
Senior sergeant Jeremy Field, of Counties Manukau police, said: "This sort of behaviour is not tolerated in the community. Everyone who attends sporting events like this needs to be safe and feel safe while attending."
Both schools were co-operating with police, he said.
Otahuhu College principal Neil Watson — who was not at the match — said he was "appalled" by the "inexcusable behaviour".
"I have never come across anything like this in my entire career."
Officials from Tangaroa College could not be reached for comment.
Yesterday's scenes come just two weeks after an 11-year-old boy allegedly tackled a referee to the ground, then punched him, during a club game. He will face an ARU judiciary next month.
