Fear this: The follicles on your head can reveal the folly of your ways, especially if you are into drugs.
Long before the Central Narcotics Bureau (CNB) began using hair-sample analysis to detect drug use, such tests were already striking fear in students from international schools in Singapore.
The CNB has been using hair samples on ex-drug abusers serving out their compulsory two-year supervision order since May.
But, say insiders, international schools here have long been carrying out such tests on its students and sending the samples overseas to detect drug abuse.
William (not his real name), a student at an international school here, told The New Paper: "The drug tests are very random, you never know when its coming.
"In most cases, you are just pulled out of your classroom and tested under supervision."
Youth drug abusers are a growing concern, although they account for the smallest percentage of arrests, according to CNB statistics.
For the first half of this year, 83 of the 1,790 drug abusers arrested were below the age of 20.
Less than 10 per cent of those arrested below that age are non-locals, said a CNB spokesman.
It is not known when international schools here began using such tests but The New Paper reported in 2004 that schools such as United World College of South East Asia (UWCSEA), the Singapore American School (SAS) and the Tanglin Trust School conducted such tests.
UWC, for example, said in the report that it conducts both urine and hair tests.
Urine samples are sent to Australia and the hair samples are sent to the US.
Random drug testing, which includes sampling strands of hair, is a powerful reason to say no to drugs, said William, a 17-year-old Briton.