Youth Court judges have expressed reservations about a law change that would extend their jurisdiction over children aged 12 and 13.
Parliament's social services select committee is considering submissions on the Children, Young Persons and their Families Amendment Bill.
As well as extending the jurisdiction of the Youth Court, the bill would also introduce tougher sentences.
Principal Youth Court Judge Andrew Becroft told the select committee on Wednesday that the change is not needed.
He says there is no quantatative research since the youth justice system began as to whether top-end Youth Court sentences work.
Judge Becroft says necessary changes to the youth justice system could be made without changing the law.
He says one benefit of the bill is that it has prompted debate about what should be done to deal with offending by young people.