In my own opinion I believe that Bruno (the kid in the boy with the striped pyjamas) is in prison because the clothes he is wearing looks like he is in the prison also because he has a number in the corner of his clothes. In one of the picture it seems like the fence is on its own and there is no one to be with.

PREDICTION 2

in then last picture it looks like they have no washer machines and that is all they wear even to weddings and funerals

there is barbed wire in there because the boy might of tried to escae thwe prison and got him self stuck on the sharp and dangerous barbed wire

the importance of the number on there shirt is that so they dont escape the prison and so they will not some how go missing

the stains on the top is so we all know what they have and what they do not have than we have now and then