New research casts doubt over whether drug and alcohol education programmes for school children actually work.
In a soon-to-be published paper, researchers say the programmes are not effective in reducing substance-related harm.
The Centre for Social and Health Outcomes Research and Evaluation at Massey University, which conducted the review, says the school-based programmes do a good job giving pupils information.
However, it says the problem is that a quite small intervention in the classroom is really trying to change behaviour that is deeply embedded in society.
The centre suggests the Government look at more cost-effective ways of preventing harm related to drugs and drink.