Year 8 pupils at Ysgol y Preseli, Crymych, Pembrokeshire, are running a campaign to encourage shopkeepers not to sell cigarettes to young people.
They consulted local retailers, parents, teachers and older pupils, and designed a leaflet and a poster. The publicity material will be used by local authority trading standards officers and will also be available to their colleagues throughout Wales. The pupils' campaign is backed by the county council as well as Pembrokeshire NHS Trust.
John Thomas, chairman of the county council, said: "Appealing to retailers to adhere to the law is an important step in helping children think twice about smoking."
The pupils also dressed shop windows for No Smoking Day. One youngster said: "It is a good idea not to sell cigarettes to children under 16 and those older than 16 should be issued with ID cards to show to shopkeepers."