A drug testing trial was carried out at a school in England

The assertion came after the Headteachers' Association of Scotland (HAS) backed calls from a drugs expert to introduce random checks.

General secretary Bill McGregor said testing pupils should be an option.

He said: "If there is a possibility of a deterioration in the drugs scene then drugs testing should not simply be ruled out."

According to The Scotsman, Professor Neil McKeganey, the director of the Centre for Drug Misuse Research at Glasgow University, told a conference that the time had come to consider widespread drug testing in schools.

Speaking in Edinburgh to senior police officers, social workers and government officials, he said pilot programmes should be developed in Scotland to find out if it was effective or not.

There should be an ability to drug test if required Bill McGregor HAS general secretary

Prime Minister Tony Blair announced plans to introduce random drug testing two years ago.

A government-backed pilot scheme in secondary schools in Kent has already begun.

Pupils are randomly selected by a computer to take a mouth swab which is then tested for drugs including cannabis, heroin and cocaine.

However, the UK Government's drug advisory panel is expected to recommend that school drug testing be abandoned because of ethical concerns and a lack of evidence that it proved effective.

Mr McGregor said there is a risk that the drugs problem in society could cross into schools.

Taking drugs

He said: "We do not believe there is a problem inside Scottish schools.

"We do accept there is a problem in the community and we are very keen to keep that problem, wherever possible, outside of school.

"Where there is a community of a school in agreement and where the local authority has given its agreement then, if necessary, there should be an ability to drug test if required."

An executive spokeswoman said: "When we last asked head teachers if they wanted these powers there was no demand for them.

"If any head teacher has concerns that a pupil might be using drugs they should involve the police, as the police are trained in the most appropriate procedures for detecting whether someone is carrying or misusing drugs."

Several independent schools have used testing as a condition for readmission for pupils expelled for taking drugs.

In another development a new DVD to educate schoolchildren, teachers and families was launched on Wednesday.