Five pupils at a Cornish school needed hospital treatment after experimenting with a cocktail of medicines.
The pupils involved are to be disciplined by the school
The youngsters, from Mounts Bay School near Penzance, had taken the prescription tablets, mainly sleeping pills, into school with them on Wednesday.
The Year Nine pupils had just completed a drug education course.
The school says it is taking the incident extremely seriously and those involved will be disciplined.
The pupils were taken to the Royal Cornwall Hospital for tests. They were then released with no major effects from the incident.
The manager of the Cornwall and Isles of Scilly Drugs and Alcohol Action Team, Bob Crossland, says that this incident has to be seen in the light of continuing effective drugs education across the county.
He said: "It is unfortunate that this happened immediately after a drug education session.
"What is important is that we look at what happens within all schools, not just this school.
"The drug action team has been working quite hard to be able to ensure that what we give to teachers are good quality resources to enable them to deliver drug education."