One of the oldest tricks drug-dealers use to get users hooked is giving out free samples.
A similar tactic is being used by a health-testing company offering UK schools free drug-detection kits in the hope they will become regular customers.
Preventx, which is based near Newcastle, said it had more than 2,000 kits to provide for schools which applied for them.
Last year it received enquiries from nearly a thousand schools, more than 250 of which bought kits.
The free kits, which normally sell for pound;7.99 each, provide single tests to detect six of the most common drugs: cannabis; cocaine; amphetamine; benzodiazepines, such as the antidepressants Valium and Xanax; methamphetamine, commonly known as speed; and morphine, from which heroin is processed.
Teachers need to collect a urine sample from the pupil, then dip in sticks which test for each drug and indicate a result three to five minutes later.
Michelle Hart, a director of Preventx, said schools might find the company's other products, which use oral swabs rather than urine samples, more practical with pupils . "We supply a high percentage of our kits to private schools, but state schools sometimes cannot afford them," she said.
"The Government has to realise that something should be done to tackle an already escalating problem."
Ms Hart said that the firm did not believe that pupils should be made to take the tests if their parents did not wish it and felt students who tested positive should always receive extra support instead of being expelled.
"Many of our customers are parents - the demand from them goes up during the summer holidays," she said. "For parents and schools it can be useful just to have the kit as a deterrent, because young people may not take drugs on a weekend if they know they might be tested."
Preventx has admitted it is concerned by the recommendations of the Pompidou Group, which has called for an end to drug-testing by schools.
Ms Hart said that if UK ministers signed up to the group's recommendations, the firm would have to switch focus to other products, such as its kits for detecting chlamydia andcholesterol.