One of Cornwall's biggest secondary schools is considering random drug testing on pupils as part of a zero-tolerance approach to drugs.
Helston Community College drafted in police sniffer twice dogs over the past six months after fears drugs were being brought on site.
In checks, 10 students were identified as having had possible contact with substances, although not as users.
The school said it would not go ahead with tests without consulting parents.
The school has nearly 1,800 students, including 450 in the sixth form.
Head teacher Dr Patrick McGovern said a big campus was needed to accommodate the students and 100 teaching staff.
He said: "Our concerns are that with a site as big as ours, if people wanted to bring illegal substances on here they could easily do so.
"To keep drugs out, we made quite clear through assemblies that we would use the police dogs and have done so twice."
Pc Tracey Fuller, of Devon and Cornwall Police said sniffer dogs did pick up some scents on pupils, and that some were searched.
He said: "Nothing was found on any of them, so that means they may just have come into contact with drugs somewhere."
The school is discussing the idea of random drugs tests by taking saliva swabs under new powers issued by the government.
Dr McGovern said: "We're debating that as to whether we ought to do it. We have the powers to do it, there are lots of good reasons as to perhaps why we should do, but it is really a matter for parents for the police."
Police back a tougher stance.
Pc Fuller said: "A school should be a safe environment, and we want there to be no drugs going into it.
"So if we had random tests, the message should get across not to go there."