As regards drugs related offenses in the vicinity of schools, the police can intervene on their own if they wish to ascertain the facts. In the context of an organized control inside, they will have to obtain a preliminary authorization of the head of the establishment concerned. FRAD (Anti-Drug Relay Trainers) for the Gendarmerie and PFAD (Police Trainers Anti-Drug) for the Police can also do prevention within the institutions. Contact the local unit for more information:
https://www.interieur.gouv.fr/Contact/Contacter-une-brigade-de-gendarmerie-ou-un-commissariat-de-police.