The more I watch this film (it is a horribly brutal film but compelling viewing) the more I start to wonder just who the "scum" actually are. Are they the borstal inmates... or are the wardens who are, for the most part, just as vile as the inmates themselves? I believe the film is made in such a way as to make the viewer ask themselves this very question, so what conclusions did you reach?
I think the intention is to make the viewer realise that labels are entirely arbitrary and in this case EVERYONE can be considered "SCUM", the governor and his religious bigotry and bullying punishment regimens (militaristic), the screws who are just adult versions of the inmates (for example one of them HAS to be exchanging the notes for coins and their "cut"), plus the inmates and their "beasting" of each other/top dog/daddy...Excruciating and essential viewing though right?? :)
...You can never put too much thought into something worthwhile; merely not enough...