A schoolgirl needed urgent medical treatment after she drank highly corrosive hydrochloric acid when her drink was spiked during a school prank.
The teenager sipped the potentially lethal liquid at Hounsdown School in Southampton, Hampshire, but immediately alerted teachers when she suspected something was wrong.
The girl avoided serious injury as a result of the quick thinking actions of staff.
Two pupils have been suspended while the incident is investigated.
Julie Turvey, Headteacher at Hounsdown School, told the local paper: "The school is taking this matter very seriously and continuing its investigation. A student took a sip from a water bottle into which other students had put a small amount of hydrochloric acid.
"Immediate action was taken to assess the student and the risk of serious harm. First aid treatment was administered and, thankfully, no significant injury was caused and no subsequent medical or hospital treatment was needed.
"The welfare and safety of all pupils attending this school is our priority. We have reported the incident to the Police and two students have been temporarily excluded."
The schoolgirl, who is in Year 11, raised the alarm on Tuesday after taking a sip from her drink.
She discovered an unusual taste and smell to the liquid. The child's science teacher abandoned the lesson while the girl was sent to the school medical room, assessed and given water to drink.
A group of boys thought to have been 'messing around' in the lesson were later questioned about the incident.
Tests reportedly showed the bottle was contaminated with the substance but that the concentration of the acid was low.