http://www.geograph.org.uk/
I found this quite by chance. The project opened a year ago with the aim of publishing a photograph to represent every square kilometre of the UK. 25% is already covered, and there's a clickable map to give easy access.
There is a Creative Commons licence on all images. This means that photographers grant the use of their photographs (provided they are attributed), while keeping copyright. Kent - particularly East Kent - isn't fully covered by any means, so why not contribute a photo of your school's locality?
Helen