This child took away another's life! Its that same thing if a grown man killed a woman! Yes the child doesn't understand consquences, but he/she should know better! A middle-schooler knows whats right from wrong! He knows that what ever choice he makes comes with a consquence, good or bad.
Like sending these young children to a den of lions. That's NOT good at all. They need to be rehabilitated while serving time in a juvenile institution. At that age, I don't think they have the full understanding of their choices. I don't think they know the consequences and the gravity of their immature and bad decision.
I am a firm believer that people that young can not be held fully accountable for their actions. The brain is still developing and at that age they need to be sent to a youth center where they can be taught and counseled, not just locked away. Once they are 18 they may need to be tried as an adult and then sent away to adult prison, but while they are still young that is not the solution.
I do not think criminals ages 13-14 should be sent to adult prisons simply because, they would be at increased risk for violence and abuse in adult prisons, due to the nature of the prison system. The age discrepancy means they would be more unlikely to defend themselves, thanks to the lack of muscle and size when compared to the adults in the prison system with them.