Drug tests introduced at a school in Kent earlier this year are working, says the head teacher.
Peter Walker, head of Abbey School in Faversham, reckons pupils are deciding not to dabble in drugs because of the threat they could be tested.
So far 64 pupils have taken part in voluntary tests and no one has been shown to be using drugs.
Every week 20 pupils are randomly chosen by a computer to be tested for drugs including cannabis and ecstasy.
The samples are sent to a lab and results returned three days later.
Less peer pressure
Mr Walker says pupils have been discouraged from taking drugs because of the risk of getting caught.
He also thinks students are using the tests as a way of avoiding pressure from other children to take drugs.
"Maybe young people have been looking for an acceptable way to be able to say no to their peer group without losing face," said Mr Walker.
Most parents have agreed to let their child be tested - and so far, only two pupils have refused.
Those picked to be tested are asked to go to the sick room and have a sample taken from their mouth - a bit like wiping a cotton wool bud inside your cheek.