Thieves have stolen specialist power tools worth several thousands of pounds from the construction site of the new Falmer Academy.
The theft is believed to have taken place from the site in Lucraft Road, Moulsecoomb, overnight on Friday and Saturday.
Construction staff arrived at work at the site at 6.45am on Saturday to find that a number of tool boxes had been opened and tools removed.
Sussex Police said that the thieves had targeted the most expensive power tools, ignoring less valuable ones.
The tool boxes were very well secured and it is believed that the break-in was planned rather than opportunist.
Police also said that the means of opening the tool boxes would have been quite noisy.
Detectives have asked anyone who saw or heard anything suspicious in the area between 6pm on Friday and 6.45am on Saturday to call 0845 6070999.