A child has been taken to hospital and another six children are being assessed for chemical exposure after a science experiment went wrong at Concord High School on Tuesday morning.

The children are reportedly suffering from dizziness and minor respiratory difficulties.

Seven children are being assessed for chemical exposure. Credit:Darren Pateman

NSW Ambulance and NSW Fire and Rescue services were called to the Stanley Street school at 10.15am to respond to a "hazardous materials incident".

Six ambulance units are responding to the incident; two NSW Fire and Rescue Hazardous Materials units have also since arrived at the school.