ACK-shually...
By the time a person is somewhere around their mid-single digit age, their core values are already pretty much established. The rest of their early development, up to about the time they hit their teens, is spent on interpreting the world around them and evaluating their limitations based on those core values. From that point, pier interactions have an influence, where they either develop positive reinforcement of their core values (in which case they are re-affirmed) or they run into conflicts with their core values (which leads to challenges and psychological problems as they seek to conform to conditions which go against the grain of their core values).
By the teens those core values are about as immutable as they can get. Peer pressure potentially causes a lot of problems in this area due to core value conflicts among peers.
Actually changing a person's core values is exceptionally difficult, more so the older they get. And that change absolutely cannot take place unless THEY recognize and strongly desire that change...and work very hard to do so.
These kids aren't technically "beyond help" automatically. A lot depends on their core values, issues they're going through at that state in their lives, and whether or not they WANT to change.
If their core values revolve around manipulation, lying, and various anti-social behavior in general, then the odds of them actually changing are much lower.
Psychologists say that for a person whose core values are developmentally set, it takes a MAJOR event in the person's life to put them on the path where they WANT to change. It can be health issues, loss of a loved one, and yes...run ins with serious legal consequences. And even then, it's a hard battle that for some may never see an actual "end".