Juveniles who commit violent crimes should be tried as adults in the court system. Violent crimes are not only particularly harmful to the victim but also to the victim's family and the community of as whole. A juvenile who commits a violent crime does not deserve a reduced sentence or any limitation on the conditions and terms of their sentence.
I believe the first time a child encounters the juvenile justice system they should be given the benefit of the doubt. On the second occasion they should receive punishment to the point that they should reconsider there ways on interacting in society. If they come back a third time and they are displaying violent tendencies, they should be treated as adults because they are acting like an adult.
I think there are situations where a juvenile offender should be treated as an adult. I don't think simply violent should be the way to decide though. I think you need to consider age, motive, crime, and history to figure it out. It should be done on a case by case basis.
Kids and teens are not fully developed in their self control and impulse control. Just because they are violent now, it does not mean this behaviour will not improve significantly when they get older.
There needs to be consequences for their actions but these consequences need to be age appropriate.
I think juvenile offenders should not be treated as adults unless the crime is so heinous and terrible that they deserve to be locked away the rest of their lives. The human brain does not completely form until you are about 25 years of age. This should always be taken into consideration.