I hate when parents do that. If your child is really a decent child, don't send him into a lions den - juvie detention. Cavalier parents with no understanding of juvie detention think they're being responsible when they help the state by making their kid confess to crimes.
Juvie detention is prison and the kids there aren't nice. Many of them are hardened seasoned criminals. They WILL hurt your child if he doesn't become a thug himself. He may learn some new tricks you do not want him to learn.
In the future, consider getting him a lawyer; even a juvie public defender.
Cross your fingers that they never charge him.