Principal Youth Court Judge Andrew Becroft told the conference that 70 per cent of the most serious youth offenders were not in school, and if there was a "magic bullet" to reduce youth crime it would be to keep them in education.
He said Maori made up only 19 per cent of the Youth Court's 16- to 19-year age group, but 49 per cent of youths caught by police, 55 per cent of Youth Court defendants and 66 per cent of young people in custody.
"The figures are unacceptable in any civilised community," he said.
The Ministry of Education has been working with the schools with the highest exclusion rates to reduce exclusions, particularly for Maori and Pasifika students.
Ministry northern regional manager Bruce Adin said three clusters had been formed in central-west Auckland, Waitakere and Whangarei where schools work together to take in any students kicked out of any other school.
Mt Albert Grammar School principal Dale Burden, who leads the central-west cluster, said his seven schoolshad reduced the average time before an excluded student was picked up by another school from 90 days to 27 days.
A coordinator keeps tabs on how many students each school expels and takes in.
"So if five are excluded from Lynfield, there is a general expectation that they will take five, and kids get shared around," Mr Burden said.
But he said one local school which excluded the highest number of students refused to join the cluster.
"They were effectively flooding this area," he said.
Youth Law data show that the five schools that excluded the highest numbers of students from 2005 to 2009 were all in Auckland: Avondale College, Onehunga High School, Massey High School, Rosehill College and Manurewa High School.
"We would have particular concerns about those five schools," Mr Mills said.
But the highest exclusion rate per thousand students in 2010 was at Queen Elizabeth College in Palmerston North, the lowest-decile secondary school in that city with a roll that has shrunk over 20 years from around 1000 to 200. Principal Michael Houghton said he took a hard line because of a behaviour problem at the school.
He made a ban on drugs "non-negotiable" and drugs were the biggest cause of exclusions.
Massey High School principal Bruce Ritchie said he also had "high expectations" of his students. But he has recently brought in outside agencies to give "wraparound support" to students and their families to try to keep students in school.
"I think it's had a bit of an impact already this year," he said.
Mr Ritchie and Mr Burden both suggested that the high exclusion rate for Maori students reflected their frequent moves.
"The transience rate is higher for Maori than for any other ethnic group," Mr Ritchie said.
