Schools in England are getting better at educating children about illegal drugs, a report from inspectors says.
Drugs education has improved since 1997, Ofsted said
England's schools inspectorate, Ofsted, found such education had improved in most schools since 1997 and that pupils had a greater understanding of drugs.
But inspectors warned that schools might be missing the mark by focusing on illegal drugs rather than smoking and alcohol, which worried pupils more.
Few schools were interested in random drugs testing, Ofsted found.
Ofsted was asked to check on the state of drugs education since it was last reviewed in 1997, particularly following new guidance issued last year.
The study was based on visits to 60 schools plus evidence from 200 school inspection reports.
Generally, the report is positive, saying 80% of primary schools, and 90% of secondaries now have a drugs education policy.
But about one in 10 schools did not devote enough time to drugs education. Inspectors said schools should do more to reflect pupils' concerns and needs. While teachers and parents were more concerned about illegal drugs, young people themselves regarded tobacco and alcohol as the greatest dangers.
The chief inspector of schools in England, David Bell, told BBC Radio Five Live that few youngsters would go on to abuse hard drugs but many came into regular contact with alcohol and cigarettes.
He explained why drugs education was important: "It's about giving young people information and also it's about helping them to make an informed choice.
"Young people are clearly going to make the decisions they make but let's ensure that they do it on the basis of good information and good knowledge so they don't feel compelled by their friends of whatever to engage in activities that are actually going to be risky to their health and often their safety."
Most schools were against random drugs testing and sniffer dogs, inspectors found and had little desire to follow the few experiments taking place.
The guidance released last year endorsed head teachers' rights to use sniffer dogs and drug testing - but suggested that schools should only do so if parents and children consented and then in targeted circumstances, usually with the involvement of police.
Martin Ward, deputy general secretary of the Secondary Heads Association (SHA), said: "SHA does not encourage its members to make use of dogs or random searches, in most schools either would be an over reaction."
Schools had been warned there was a danger they could breach children's human rights if they did not get consent for such tests.
On the suggestion that schools should spend more time on drugs education, Mr Ward said the school day was already crowded.
The Children's Legal Centre at the University of Essex said it had only heard of three schools in England where random tests were being carried out.
They all seemed to have followed government guidelines on consent.
The general guidelines quote research that says about a third of 15 year olds are using cannabis.
Schools Minister Andrew Adonis said drugs could have a devastating impact on young people's lives and that the majority of children had never used an illegal drug.
"We have equipped heads with a comprehensive range of approaches to tackle drugs, alcohol and tobacco in their schools, even up to the use of sniffer dogs or drugs testing," he said.
"Of course, heads are best placed to determine which approaches are best for their schools, and we trust them to make the decisions that are right for their schools."
Jenny McWhirter, from DrugScope, said the charity welcomed the report's findings of improvement in drugs education.
However, she called for drugs education to be part of basic teacher training and for more effort to engage parents and carers more fully in the programme.