POLICE were called into an Accrington high school after cannabis was found on three pupils.
The students, all boys, were arrested, quizzed by police and given reprimands.
The incident, which took place at Mount Carmel, was revealed this week in an e-mail sent out by police to key community figures across the borough.
Community beat manager Mick Walsh praised staff at the school for their quick thinking and decisive action.
He said: "Due to the swift actions of the head Miss Katrina Ryan and her staff, the pupils were detained and arrested. We discovered a small amount of cannabis on the three pupils and it has now been destroyed."
Miss Ryan said the school adopted a zero tolerance approach to drugs and she was working with the police to raise awareness of the issue through a pilot scheme called Blueprint.
She added: "This is the first incident we have detected in school. We have a very good relationship with the police and Mick Walsh in particular."
One of the students has been suspended and will only be allowed back in school to sit his GCSE exams. The other two boys were temporarily suspended and have now been allowed to return to lessons.
Miss Ryan added: "We have carried out a thorough investigation with senior staff and the police. The parents have all been involved and we have spoken to all our students. We reinforced the message that drugs won't be tolerated."
PC Walsh added: "The three students were given a reprimand, which is a warning to them. If anyone is under the age of 17, they receive two reprimands and then a final warning before court action can be taken."
He added that both he and PC Simon Challenger were working with the school under the Blueprint project to raise awareness of drug issues. The project involves around 25 schools across the country.