Scum refers to the label slapped upon reform-school inmate Ray Winstone. Such reformatories are called "borstals" by the British. When he isn't being beaten up by the other boys, Ray is being beaten down by The System. He rebels against this treatment and "wins" by becoming more vicious than any of his oppressors. Scum was originally filmed for British television, but rejected because of the bleakness of its outlook. In America, it went straight into theatres, where audiences had to strain to comprehend the "punk" jargon and thick provincial accents.
~ Hal Erickson, All Movie Guide