Schools have been clamping down on vaping following a rise in kids using e-cigarettes since the pandemic.
Teachers have been left frustrated by the attractiveness and availability of the products to teenagers.
At Ysgol y Strade in Llanelli, Carmarthenshire, staff patrolling the grounds at lunch time have a zero-tolerance approach.
Pupil caught vaping are excluded, with further punishments for repeat offenders.
Before Covid lockdowns, vaping was not a big issue for schools, but the 1,300-pupil Ysgol y Strade, like others, saw things change when pupils returned.
Two years ago it decided to introduce tougher sanctions and raise awareness of the rules and the risks of vaping.
Assistant head teacher, Daniel Hughes, said the number of children caught with vapes had fallen "substantially".
First time offenders usually get excluded for one day, after which the number increases.
