Police were called to Newcastle College on Knutton Lane following a report of a potentially "hazardous substance" being found.
The discovery was made in the science block. As a precautionary measure, two floors of the school have been evacuated.
Officers from the military Explosive Ordnance Disposal (EOD) were called to the scene to investigate.
According a police spokesperson the substance was disposed of and there is no risk to the general public.
Staffordshire Police are thanking the people for their patience while they dealt with the matter.