I've worked with young offenders. Some of them had committed pretty nasty crimes. The crimes these children committed were evil, no doubt about it.
Just because it was interesting to me, here are the things that I noticed in years of working with 'scumbags'. When you went through their lifeline, there was, more frequently than not, a bereavement. Mother, father or sibling. I haven't seen a lot of discussion about that in offending circles but it struck me.
Also, walking into a classroom with them... 8 of them could create more bedlam than 30 in a classroom outside. Not the same with the female offenders at all. Very obviously, there were massive levels of learning issues. FASD, ADHD and so on. When they were given learning support (only inside of course) they all did very well.
Lots of self harm. They don't just not care about other people's pain, they don't care about their own. Drugs, drink, cutting, suicide attempts, unsafe sex you name it.
I'm not saying any of this justifies extreme violence. What I am saying is that these children don't some to this like your children would. They have already suffered so suffering is unlikely to change them into upstanding members of society.
BTW, I'm biased. One young offender saved me from, at the very least, severe burns, possibly I could have died.