I believe it is possible to identify dangerous people, both teenagers and adults long before they become a threat to society.
I have many teachers in my family and among my friends. Especially those who have worked with young children, are quite willing to admit that they can identify psychopaths at an early age.
They are almost universally convinced that the behavior of the child who is a psychopath and a future danger to society is readily detectable to most teachers.
To my knowledge, no one has attempted to figure out how such observations could be turned into a functional social instrument.
I know that in Japan, where I have observed children under six in large groups, that children up until that age have been leading lives of almost unrestricted freedom.
The Japanese approach seems to be to use this period to develop and expose the child's character. I assume the purpose was to help create workable marriages later in the person's life by making appropriate matches. Something feasible in a small community.
I have no idea how the Japanese deal with a psychopath. But since there seem to be so few adult psychopaths I assume that these children get intense care and focus to generate appropriate socialization.
I would not trust our society to make records of young kids who are psychopaths. Teachers may not be reliable, the mechanism for correcting errors in the transcript may not be reliable and no one should face a life of prejudgment.
Nevertheless, I do think the subject warrants consideration and discussion.