Oh, AllieKat, I'm so sorry to hear this. You are absolutely not the first user who has come here in a similar spot, and I am glad to do whatever I can to help support you now. I/we are also glad to do whatever we can to help support you as you get ready for your time in juvie, and, if you have any access while there, while you're there. No judgments here about any of this. I myself didn't spend time in juvie, but only because I got lucky, and I did wind up in other not-dissimilar spots. I had lots of friends who wound up there, and I've also worked with a lot of youth who have spent time there. I understand how you're feeling, but please know that the harshness you're feeling for yourself right now isn't a way *I* or we feel about you or this situation, okay?
This may or may not be helpful to you, but this probably wasn't about being stupid. You know, during some of adolescent development, there's a part where part of your brain just isn't super-duper when it comes to impulsivity and decisions. Like, it just isn't cooked yet when it comes to that, so it's really easy to wind up in these kinds of spots, and too feel like your decision-making is something that happens faster than you can control, and happens in a way that, in hindsight, just doesn't look like something you'd even do when it's slowed down in rewind.
Here's a thread from another user that wound up in a similar spot that might both have some practical information you might find helpful, but also might help you feel less alone: viewtopic.php?f=14&t=8089&hilit=juvie#p41117
I'm here for another few hours today working on some editing, so I am happy to listen some more, and talk however you'd like to. We can talk practical things or feelings or both, we can talk about juvie coming up, about life after, about your feelings around your parents and family, about friends: whatever you need. <3