The comments follow new research linking ongoing cannabis use before the age of 18 to a decline in intelligence.
Mr Gibson said the findings were especially concerning for those working with at-risk youth exposed to drugs.
The report, published in the Proceedings of the National Academy of Sciences, analysed more than 1000 New Zealanders.
It found those who started smoking cannabis during adolescence, and were diagnosed as being addicted by age 38, experienced an average decline in IQ of eight points from the age of 13.
Those who began smoking after age 18 - and after their brains had developed fully - did not show a similar decline. The Secondary Principals Association says cannabis use among young people and its effect on learning is an increasing concern for schools.
"Since the introduction of zero tolerance for drivers [under 20] - who are not allowed to drink any alcohol at all - we've noticed that some students ... or teenagers are switching to the use of cannabis because that's not detected," association president Patrick Walsh said.
Schools were struggling to address the problem of cannabis use by students - who often experienced short-term memory loss and lacked motivation once they started using.
"We have reports where students take up the marijuana habit at the age of 12 or 13.
"It certainly affects their learning."
According to the United Nations, New Zealanders have the highest rates of cannabis use in the world.
Some schools already carry out random sniffer dog testing for drugs.
But Mr Walsh said if young people were switching to cannabis because it could not be detected during roadside breath testing, "then I think drug testing needs to be seriously considered".
Social Development Minister Paula Bennett announced compulsory drug testing for beneficiaries earlier this week. Under the scheme, which will take effect next July, beneficiaries who fail or refuse drug testing when applying for jobs will have their welfare payments stopped.
They will also have to reimburse the cost of the drug test.
