Two kids commit the same crime. One gets a break and is tried and sentenced in the juvenile justice system. The other is tried and sentenced as an adult. What happens?
The kid who was tried as an adult is 34% more likely to commit a crime when released (American Journal of Preventive Medicine citation here).
But, doesn't keeping the kid who was tried as an adult make the juvenile justice system safer? No.
Yes, I'm fully aware of the argument that the really bad people, based on factors harder to observe from a distance than the offense charged, are the ones charged as adults, thus explaining the difference in recidivism rate. If you believe that is true, I urge you to do a study supporting that claim. I'm not aware of any such studies. My anecdotal experience is that the decision to charge kids as adults has more to do with the politics of the people making the decision than the detailed circumstances of the offender. Indeed, detailed offender information is often not known very well in the early stage of the process where this decision is made in states like Colorado where prosecutors, rather than judges, usually make the call.
Trying juveniles as adults doesn't make us safer. It just makes us feel better when we read the paper.