James Kenney, who I've seen in several movies, gives an outstanding performance of this young undisciplined hoodlum whose hysterical vileness and strutting arrogance propped up with a false bravado that finally cracks like a mirror at the end of the film....well, crime couldn't be shown to pay, could it? And yes, the police of that time were quite willing to let parents or guardians punish their young 'uns if they thought it would do any good. Parents would insist to the policeman, "Leave him to me!" if he brought shame on the house...I know! Alternatively the policemen themselves would give you a clip on the back of the head with their hand (painful) or flick you with a rolled up cape on the bum (very painful). You wouldn't go running to your Dad crying about it for he'd give you another clip saying you must have deserved it.
Social history tells us of how Britain, with four million men in uniform during the war years saw a generation of youth largely grow up without the guidance of fathers or older brothers. Juvenile delinquency figures during and after the war went through the roof and with many de-mobbed soldiers bringing looted pistols and revolvers home with them there was a steady supply of weapons filtering down to the criminally-inclined classes, and resulting in a massive increase in crimes of robbery, assault and murder by those who were 'tooled-up' and who were quite willing to kill their victims rather than let them live to identify their attacker and possibly end up making the acquaintance of Mr Pierrepoint and his neck-adjusting service (which he performed...on a career-best 405 occasions!).
For the time, and of the time, Lewis Gilbert's film stands up well in my eyes compared to the rose-tinted comedic films depicting similar disenfranchised youth such as the funny 'Hue and Cry' which I also enjoyed enormously.
Taking a film out of its time-period to deliver judgement can't be right.
There were many films made back then (and even now) that are shoddily made with poor acting, dire scripts and non-existent production values that deserve all the brickbats they get, but 'Cosh Boy' isn't one of them....in my humble opinion.