Wanganui schools have stood down, suspended or permanently excluded misbehaving pupils more than 600 times this year.
But Education Ministry figures released to the Chronicle show the number of disciplinary cases for drug offences has fallen since 2009.
A Wanganui school principal says student drug use tends to revolve around the cannabis-growing season.
"There are certain times around the growing season where obviously people are trying to sell it and kids can become targeted," Cullinane College principal Kevin Shore said.
Mr Shore, who has been teaching for over 20 years, said drugs had been a constant problem in schools. "But I don't believe it's any worse [now] than it's been in the last 10 to 15 years."
Stronger anti-smoking attitudes and increased understanding around the harmful effects of drugs seemed to have discouraged drug taking locally, he said.
The number of students disciplined for drug offences has fallen since 2009, the figures released under the Official Information Act show.
Local schools have stood 600 pupils barred from school this year down, suspended or excluded pupils 18 times this year for drug-related offences. Two pupils were permanently dismissed.
More than 600 disciplinary cases occurred across the region during the period.
Mr Shore said a variety of approaches were used to deal with students found or suspected of taking drugs at Cullinane College. There had been no such cases in the last six months.
If a student was found with drugs, their families were contacted and drug and alcohol counsellors could be called in.
Nationally, schools stood down, suspended or permanently excluded misbehaving pupils more than 17,500 times between January 1 and October 16 this year. Nearly 2000 student disciplinary cases involved drugs.
About 10 per cent resulted in pupils' permanent exclusion or expulsion.
Secondary Principals Association president Patrick Walsh said though numbers had fallen in recent years, drugs remained a serious issue.
Cannabis was the most common drug, but more students were using synthetic cannabis products or "party pills", he said.
Case numbers peaked two years ago. More than 3000 disciplinary incidents involving drugs were reported to the Education Ministry, with more than 350 students permanently excluded.
This was up from about 2700 cases in 2009, which had included 262 expulsions or exclusions.
However, Mr Walsh warned that drug problems in schools had not diminished.
"It's just being masked because schools are dealing with it in different ways."
More schools were now using restorative justice programmes before stand downs or suspensions, Mr Walsh said.
He also warned of the effects drugs had on students.
"Often they have short-term memory, they can become aggressive [and] socially isolated."
General lethargy, a lack of application to studies and disengagement with co-curricular activities such as sport were other common side-effects, he said.
Definitions
Stand down: removal of a student for a period of up to five days. Decision is made by the principal.
Suspension: formal removal of a student from school until the board of trustees decides the outcome at a meeting. The board can extend or lift the suspension, or terminate the student's enrolment.
Exclusion: Permanent termination of a student, aged 15 and under, from the school.
Expulsion: Permanent termination of a student, aged 16 and over, from school.