It occurred between 7.30pm and 8pm on Sunday 26 May 2013, at Thirsk Comprehensive School, Topcliffe Road.
Vandals used stones and pieces on concrete to break 10 windows on the ground and first floors. They also damaged a handrail and left it on a roof.
PC Quita Passmore, of Thirsk Safer Neighbourhood Team, said:
I need to speak to anyone who can help to identify those responsible for this mindless act of vandalism and urge them to contact the police straight away.
I also need to speak to anyone who was in the area of the school around the time of the damage and ask that they get in touch.
I am also reminding people that it is extremely foolish to go onto a building’s roof. It could be dangerous for anyone who does not know what they are doing or without the correct safety equipment. Anyone falling from a roof may suffer a serious injury, if not worse.
Anyone who can assist with this enquiry is asked to contact Thirsk police on 101, select option 2 and ask for Quita Passmore. Alternatively information can be emailed to email@example.com
Or call Crimestoppers anonymously on 0800 555 111 quoting reference number 12130084715.