Around a third of UK adults have tried illegal drugs, mainly cannabis, suggesting that 160,000 teachers in England and Wales may have dabbled.
Nigel de Gruchy, general secretary of the National Association of Schoolmasters Union of Women Teachers, believes politicians are afraid to grasp the nettle, despite polls showing support for decriminalising the 'soft' drug.
"It's hypocrisy for society to say teachers have special responsibilities while everyone else can go and get drunk or stoned. If a cannabis-taker can end up in the Cabinet, why can't thy end up in a classroom?" said Mr de Gruchy.
None of the teaching unions, including the NASUWT, has endorsed decriminalisation. But society's ambivalent attitude towards cannabis is reflected in responses from the Universities' Council for the Education of Teachers, headteachers, LEAs and governors, who told The TES they would be likely to take on a teacher even if they had a teenage caution for possession.
A recent conviction or caution while in post would be more likely to result in disciplinary action, and possibly dismissal. All drew the line at dealing or hard drugs.
A Department for Education and Employment spokeswoman said some teachers on list 99 (a Government blacklist) have been debarred for drug convictions.