Three pupils at Park Primary School in Bargoed have created posters telling smokers not to drop their cigarette butts outside their school.
The children have been given gift cards for their creative efforts as part of a school-wide competition.
Charity Groundwork Caerphilly and Gwent Police worked with the school to help organise the competition.
Brogan Mills, aged 10, won first prize and will see her posters on fences outside the school to remind smoking parents that dropping cigarette butts is littering.
Tiana Fortune and Jake Richards were also awarded gift cards for their posters.
Janine Reed, an officer for Groundwork Caerphilly, said: “All the entries by the pupils were of a very high standard and we want to thank the students for their help in keeping Bargoed a clean and tidy place, free of cigarette butts.
“Smoking is not just bad for your health, it damages the environment. Even after someone has finished a cigarette, if the butt is dropped on the floor it can affect surrounding wildlife. If swallowed, animals are unable to digest this litter and this can prove fatal.”
PSCO Lisa Humphries, said: “We were really impressed by all of the competition entries that the children submitted. The posters have now been displayed around the school, and we hope that they act as a reminder to parents that they have a responsibility to keep the area litter free.”
The prizes were donated by the Greater Bargoed Communities First Partnership.