Nothing could be further from the truth. There is no profound lesson to be learnt from Mary Bell, nor from her story, nor indeed from the instances of children who kill. Children kill about once every 10 years in this country. Explaining why Mary Bell killed is a fool's errand. You might just as well try to explain why schoolboys dangle out of windows or why infants throw their toys around.
Childhood is in many ways without reasons.
The depressing truth is that it was just Mary Bell's bad luck that she went that bit further than torturing the cat or the budgerigar. Perhaps looking back over Mary Bell's life now it seems obvious that she was on a course of destruction. But then lots of people had terrible childhoods and never killed anybody. Everybody's life looks like fate when viewed in retrospect - you always think you can identify that influence which made you needy, gay, competitive or whatever. But you are just kidding yourself.