Amsterdam's mayor said he would formally ban students from smoking cannabis at school, making the city in the Netherlands the first to do so.
Eberhard van der Laan's introduction of a law is the result of the country's drug policy. Under the "tolerance" principle, cannabis is technically illegal in the Netherlands, but police cannot prosecute for possession of small amounts of the drug.
The loophole has made it possible for Amsterdam's "coffee shops" – cafes where the drug is sold openly. But it has also led to Dutch children being frequently exposed to cannabis in public areas.
A city spokeswoman, Iris Reshef, said schools have always forbidden cannabis, but found it difficult to enforce the policy when students smoked on or near campus.
"It's not really what you have in mind as an educator, that children would be turning up for class stoned, or drunk either for that matter," she said. "But it has been a problem for some schools."
After a change in national law, the city will now be able to declare as of 1 January "no toking zones" – areas such as schools and playgrounds where consumption of cannabis is forbidden – under a public nuisance ordinance. Police can then levy fines against students or anybody else who flout the rules.
The move is closely paired with a decision by the new government to ditch plans for a national "weed pass" that would have blocked tourists from buying cannabis.
That was a measure years in the making, and greatly desired by cities such as Maastricht that have been flooded with dealers from Belgium and Germany who drive across the border to buy cannabis in bulk. But the weed pass was opposed by Amsterdam, where drug tourists are not generally seen as causing a nuisance.
Last month, Van der Laan proclaimed that coffee shops would stay open for tourists after all. In a letter on Wednesday, he noted that one-in-three tourists who come to Amsterdam try cannabis while they are there, more than previously estimated.
Wednesday's decision means the drug will remain available for adults and tourists who want to try it, but access for children will be restricted.
After several decades of the tolerance policy, Dutch cannabis usage rates are in the middle of international norms, higher than those in neighbouring Germany, but lower than those in France, Britain or the US.