Pupils who feel under pressure to achieve better results at school are more at risk of turning to drugs, teachers warned.

The Professional Association of Teachers said there was a strong correlation between disaffection with education and drug abuse.

David Blunkett's new cannabis policy is sending mixed messages on drug use to young people in particular

Peter Gemmell, PAT delegate

And the government's decision to decriminalise cannabis had only sent a mixed messages to young people, said delegates at the union's annual conference in Telford.

"There is a very strong link between drug use, and obsession with drugs, exclusion from school, or disaffection within school," said Jane Lovey from Cambridge.

"There is no doubt that for many pupils, for whom school has little joy to offer, their first experience of smoking cannabis, crack cocaine or heroin, is a wonderful one."

'Low self-esteem'

Mrs Lovey, who researches the impact of drug awareness policies, interviewed children in six areas of England that took part in a survey of local education authorities by the charity Drugscape.

One boy who was being bullied described his first encounter with cannabis as "great, suddenly I had no worries, all the pain and fear had gone. I was happy, I couldn't wait to do it again", said Mrs Lovey

"He also expressed relief that cannabis is now legal."

Many of these children came from families where self-esteem had been low for "generations", she warned.

Mrs Lovey called on the government to introduce more mentors into schools.

Peter Gemmell, a PAT member from Derby told delegates: "I am sure many of you will agree with me that David Blunkett's new cannabis policy is sending mixed messages on drug use to young people in particular."

The union said teachers needed more help with drugs awareness education.