Palmerston North Boys' High school has removed three senior students from its boarding facilities after they were found with drugs.
The boys in years 11 and 12 were caught with the contraband following a regular patrol through the hostel by a drug detection company using sniffer dogs on 1 July.
The school's rector, Tim O'Connor, says the boys have not been expelled but have become day students. They are remorseful and have been offered counseling.
Mr O'Connor has not identified the drugs found, but says he wants R18 legalised party drugs added to the school's list of prohibited substances.
The rector he wants it made clear to parents and students that legal party drugs will not be tolerated at the school.