So the answer to the message in this photograph is really quite interesting. The image is from the first ever graduate class of the US Cipher school in 1918. The students, under that great cryptographer William Freidman are lined up in a novel form of the same Bacon’s code. By nominally grouping them into fives, the fives associated with Bacon’s code the can display a message. In this case rather than A’s and B’s the two code elements are ‘looking at the camera’ or ‘not looking at the camera’. The message reads (with one or two errors) a famous quote from Bacon himself “Knowledge is Power”.
Modern technology however gives you an alternate way of cracking this code. Copy the image and use google’s image search facility (a remarkable tool for today’s intelligence analyst). That will lead you, directly, to a decoded version of the image and indeed the story behind it.