Seven boys from a Lancashire high school are recovering after suffering from the effects of smoking cannabis.
Paramedics were called by the head teacher of St Augustine's Roman Catholic High School in Billington, Ribble Valley, on Wednesday afternoon.
The pupils, who are aged 14 to 16, were taken to the Royal Blackburn Hospital for treatment.
One student has been expelled and six have others been suspended. Police are investigating the incident.
Head teacher Anthony McNamara said that the pupils broke school rules by leaving the premises on Wednesday and that it was while they were off-site that they smoked the cannabis.
A letter has been sent to all parents explaining the situation.
"This is not the first time that something like this has happened at the school but such incidents are rare - the last one was years ago," Mr McNamara said.
"Unfortunately no head teacher can claim there is never any drugs or bullying in their school - you can't hermetically seal a school.
"We have 1,000 pupils at our school and over the course of five years there will be incidents like this."
Mr McNamara said that such incident would be dealt with "firmly and promptly".
"We will always deal vigorously with individuals whose anti-social behaviour puts the health and safety of our school community at risk," he said.
"Our personal, social and health education programme provides our pupils with clear information about illegal and harmful substances.
"Our police community liaison officer is a frequent visitor to these lessons."
A police spokeswoman confirmed that officers had been called to the school and were investigating the incident.