Parents are being urged to warn their children to stay away from the old Thornhill College site at Culmore Road.
The former school campus was targeted again recently by vandals who went on a wrecking spree in a number of buildings.
Local Councillor Sandra Duffy said: “The fact that these people arrived with implements to cause maximum damage is especially worrying as the buildings are already in an extremely dangerous condition.
“I am, therefore, urging parents to ensure that their children are made aware of the dangers of entering this site.
“Due to the deterioration in the condition of these buildings and lands, caused in big part by the disregard of vandals for public safety, they are not a playground or safe place for children or teenagers to congregate.
“The former school complex has been a magnet for anti-community activity over recent times. It has been subjected to numerous arson attempts and the latest attack saw materials piled up in preparation for a fire.
“However, by sheer good luck, it either didn’t take hold or the culprits were disturbed.”
Councillor Duffy urged parents to be aware of their children’s whereabouts and advise them to stay away from the site “before we are faced with serious injury or worse.”
“There is a planning application presently with Derry City and Strabane District Council for a proposed development on this site and Sinn Fein would call on the Planning Committee to move on this application as expeditiously as possible.”
Thornhill College moved into its new campus opposite the old school in 2003.