Hi-tech security marking is being used in Medway schools in a crackdown on the theft of lead roofing and equipment.
SmartWater paint, an invisible and permanent ink which is visible under ultra-violet light, has been given to every school in the area.
In 2007/8 the theft of IT equipment from Medway schools cost more than £25,000, while the bill for damage from burglary or theft was £46,000.
Kent Police said roofing material was a common target for metal thieves.
Insp Dave Coleman said: "There has been a significant increase in the value of scrap metal and in turn this has resulted in thefts of metals increasing.
"A common target for thieves is lead flashing, copper piping, plumbing material and cabling.
"Both the police and council want to make life as hard as possible for a thief and have worked together to roll out the use of SmartWater in every school in time for the summer holiday."
Medway Council, which has jointly funded the project with Kent Police, said theft took "time, money and energy" away from teaching and learning.