The Principal Youth Court Judge says every young person still attending school is one less potential career criminal.
Judge Andrew Becroft told the School Trustees Association conference in Wellington on Saturday that boards should think more carefully before they expel pupils.
He says of the 4000 young people appearing in the Youth Court each year at least 3000 are not attending school.
"A problem pupil removed, excluded, suspended even, and then on the way out, is a problem solved maybe for the school, but it's not a problem solved for New Zealand or the local community, it's merely a problem relocated."
Judge Becroft says keeping people meaningfully involved in education would go a long way towards reducing youth offending and it should be a top priority for authorities.
Mount Hutt College board member Jo Suyke, who was at the conference, agrees with Judge Becroft's comments and acknowledges her board has been too quick to expel students.
"We have made some calls over the last two years about students that we should not have let go. We should have kept them, and thought outside the square as to how we engage them."
Ms Suyke says school boards have an obligation to do all they can to avoid expelling a pupil.