Judge Becroft said it was not for him to draw any link with lowering the legal drinking age from 20 to 18 in 1999.
Massey University research has found an increase in youth traffic injuries and deaths since 1999, reversing earlier improvements, but researcher Taisia Huckle said no one had looked for a link to violent youth crime.
Comments from several speakers saying it should be harder for schools to exclude difficult students drew the loudest applause from 250 people from across youth justice agencies at yesterday's conference.
Judge Becroft said between 2000-3000 young people had been "lost" to the education system, largely because they were simply not enrolled anywhere.
"Actually, they are not lost, because we find them," he said. "They are often a captive audience, sometimes even in handcuffs.
"The Ministry of Education for so long has been difficult to engage on this issue, but it is undergoing a sea change - part of a new can-do approach.
"We have an education officer in the Manukau Youth Court to link people back to school. Where that happens, the reoffending rate is dropping spectacularly. We badly need it in Auckland and Waitakere courts, in particular."
No figures have been published yet from the trial of placing Ministry of Education officers in Youth Courts, which started in Manukau and Porirua in 2010 and extended to Christchurch last year.
Manukau Youth Court Judge Ida Malosi said the Manukau education officer rang school principals directly to get young offenders back into schools. She said schools sometimes did need to exclude students if they endangered other students or teachers.
On alcohol, Judge Becroft said the "de facto" purchase age was already much lower than the legal age of 18 - "probably 14 or so".
"If we could take alcohol out of young people's hands we could take 80 per cent of the violent offences out of the Youth Court," he said.
He showed a photograph of a 12-pack of 250ml cans of Cody's Bourbon & Cola with Raspberry, with 8 per cent alcohol content, selling for $12 ($1 a can). Bottled water was selling next to it for $1.80.
"You can't tell me those products are manufactured for the 30-to-40-year-old market for the barbecue on Saturday night. It seems to me they are explicitly made and marketed for the under-18s, and we reap the social consequences of that. In my view, it's got to stop."
A spokeswoman for Justice Minister Judith Collins said the Government had tabled amendments to the Alcohol Reform Bill to limit ready-to-drink "alcopops" to a maximum of 6 per cent alcohol content and 1.5 standard drinks.
