Unusually, not one of them uses the original photo unaltered (UPDATE: See below!). Here it is, via Getty Images and the Hulton Archive (hence the watermark), and it's a 1948 photograph by Bert Hardy. One boy is either replaced or removed, or else a new background has been dropped in.
It was originally published in the 'Picture Post', with this caption: "Gorbals Boys, 31st January 1948: Two young boys from the Gorbals area of Glasgow. The Gorbals tenements were built quickly and cheaply in the 1840s, providing housing for Glasgow's burgeoning population of industrial workers. Conditions were appalling; overcrowding was standard and sewage and water facilities inadequate. The tenements housed about 40,000 people with up to eight family members sharing a single room, 30 residents sharing a toilet and 40 sharing a tap. By the time this photograph was taken 850 tenements had been demolished since 1920."
There's a long but fascinating article on Bert Hardy here, including a theory that his Korean War photographs may have led to 'Picture Post''s downfall.
Thanks to John Self of Asylum for bringing the three covers to my attention.