Metal thieves have targeted a school in Essex four times in the past two weeks.
About half a tonne of lead was stolen from the roof of St Helena School, in Colchester, between 1600 BST on 27 October and midnight the next day.
Another 20 metre stretch of lead was stolen from the school between 1200 BST on 29 October and the morning of 1 November.
The school was again targeted the following day and on 4 November. Police have appealed for information.
'Posing as workmen'
Insp Paul Butcher said: "The individuals behind these thefts have clearly given no thought whatsoever to how much repairs and replacements will cost the school.
"We are extremely keen to hear from any involved in the scrap trade who believes they have recently been offered lead in suspicious circumstances.
"We are also keen to hear from anyone who was in the area at the time of these thefts and may have seen or heard something which could help the investigation."
He added: "We believe these thieves may be posing as workmen to reduce suspicion and it is also highly likely that the thieves are using a vehicle to transport the items away from the scenes."