This has been in a local paper round here (Southampton) and so i had to see it for myself.
On a last day of term, some leavers from Bellemoor School, Southampton "left their mark" on the school. Little did they know that imaging satellites would catch it for the world to see.
go to http://local.live.co.uk and search for bellemoor school (postcode SO15 7QU) and zoom in as close as you get over the schools field in "aerial" view
enjoy, i wet myself laughing
EDIT: it seems it might be easier to see in "Birds Eye View"