Drug sniffer dogs are to be introduced on school buses across South Yorkshire.
Random checks will be carried out on buses used by pupils
As the debate over the down-grading of cannabis from category B to C continues, police say they will arrest any youth found with the drug.
Chief Inspector Malcolm Chiddey said the move was not a threat, but intended to reassure parents and teachers that drugs in school will not be tolerated.
A police officer, along with a responsible adult will carry out the random checks.
The project is being run in conjunction with schools which belong to the Safe and Friendly Environment, a partnership between police, South Yorkshire Passenger Transport Executive and schools.
Chief Insp Chiddey said the scheme was not meant to be a frightener, but part of a wider effort to clamp down on nuisance offences on all buses used by youngsters to travel to and from schools.
"Across the six policing districts in South Yorkshire we don't want drugs on buses, or in schools, and parents can be reassured that we are working to ensure there are no drugs supplied travelling to and from schools," he said.
"This action is not a threat, but a reassurance to parents that we're working with them for drug-free travel."
And he said that a sniffer dog and officer would be accompanied by a responsible adult, usually someone from a school, on the buses.
"Where the dog indicates there may be drugs we will search that person, and if they are found in possession of controlled drugs they will be arrested.
"It is important to know that the change in the law (relating to cannabis) does not affect our powers of arrest for people under the age of 17.
"Children under the age of 17 will be arrested for possession of drugs and papers passed to the Youth Offending Team for consideration."