Ambulance crews have taken seven students to hospital after they took an unknown substance at a private northern Gold Coast school.
Emergency crews were called to Saint Stephen's College at Upper Coomera just before 1:00pm to treat multiple patients.
Four of the boys are in a critical condition, one is in a serious condition.
The boys, aged between 14 and 15, were taken to hospital in varying levels of consciousness.
Queensland Ambulance Service's Patrick Berry said tests would determine what the teenagers took.
"At this stage, we're leaning towards overdose," he said.
"We are still trying to ascertain toxicology results of what is possibly a substance that they have ingested.
He said paramedics were called after staff at the school noticed the children deteriorating.
"These boys started to become very not aware of their surroundings, one was having trouble with his consciousness, others were feeling nauseous," he said.
The toxicology results are yet to be obtained by the Gold Coast hospital
Inspector Tony Wormald said police were investigating.
"The police take a very dim view of this," Inspector Wormald said.
He said it was too early to say if the teenagers would be charged.
"We're more concerned with where they got the drugs from, why they took it and hopefully everybody pulls through safely.
"The supply of dangerous drugs to anybody is of a concern, however, in this case it's school children and we are making some inquiries into whether they purchased it off the internet themselves."
Other students are being questioned by police.
Headmaster Jamie Dorrington said he would be visiting the students later.