An intense five-month drug investigation called "Operation School Yard" led to the arrest of 25 Montreal-area high school students and four adults Wednesday morning.

The students, aged 12 to 17, were charged with trafficking illegal drugs and suspended from school for an indefinite period.

More arrests are expected as police continue their investigation.

More than 80 police officers were involved in the morning bust that was carried out calmly.

"(The students) were asked to come outside, once outside police arrested them and read them their rights," said one police officer.

Pierre Chouinard of the St-Jean-sur-Richelieu police said that drugs in schools is a growing problem and is not isolated to the two high schools targeted in the bust.

He adds that teenagers believe that since Ottawa made moves to decriminalize marijuana this year, it makes it a legal substance.

"I think the war on marijuana is lost," he said.

The investigation began a year ago after local police received calls from concerned parents and the school board.

Police know the crop is grown in nearby cornfields, but they don't how it's getting to the student dealers.