Ambulance crews were called to Four Dwellings Academy, in Birmingham, at about 10:15 BST on Wednesday.
The seven were taken to hospital as a precaution, West Midlands Ambulance Service said.
The service added the chemical was “isolated” and there was “no risk to anyone else”.
School spokesman Mike Barnett said a year 10 pupil had “inadvertently and mistakenly” opened a bottle of bromine water during a science lesson.
“The laboratory was immediately evacuated and emergency services were called to the site,” he said. “The safety and welfare of our students and staff is our number one concern at all times.”
Can science lessons become too dangerous? Please tell us your thoughts in comments or via Twitter ~ Tamsin
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