Guidelines from the Standing Conference On Drug Abuse (SCODA), launched at the SHA conference by drugs tzar Keith Hellawell, say that no single strategy is correct because incidents vary so widely.
It follows a study, commissioned by SCODA and the Government, which found only three-quarters of schools had a written policy - 88 per cent of secondaries and just 40 per cent of primaries.
Fewer than one in five had consulted pupils, parents or youth services. Ruth Joyce, past head of prevention and education at SCODA, said: "The key message is: involve as many people as possible."
The study indicates that 20,000 pupils are suspended each year for using illegal drugs, alcohol or tobacco. The 1,000 schools surveyed had suspended 1,432 and permanently excluded 378 over two years to June 1998.
Mr Hellawell told SHA delegates some heads were too eager to act tough and protect their league placing by excluding. But that would not break the expelled pupils' links with classmates.
He said the other end of the spectrum - the non-judgmental approach - was also too extreme.
Illegal drug-use has risen eight fold among 14 to-15-year-olds since 1987 with 40 per cent of boys saying they have tried cannabis, 11 per cent LSD or amphetamines and 5 per cent ecstacy.
The Right Approach: quality standards in drug education. pound;10 from SCODA, 32-36 Loman Street, London SE1 0EE, tel 0171 928 9500