It ranges from assault to run-away; what ever gets them probation. A few years ago I had a kid in my class who stole a car. Keep in mind I teach in the inner city of a city that just misses being in the top 100 in the US as far as population goes. I see quite a bit.
What for? I don't expect to actually know the answer because you may not be privy to that information, but I'd like to know what a 13 year old does to end up with an ankle bracelet.
Same things that 13 year olds do to end up in maximum security facilities like I'm a counselor in. Probation, probation violations, absconding placement, drug and alcohol issues, violent and/or sexual offenses. An unending list, really. The juvenile system is saturated. It'll continue to be a terrible problem as long as education and rehabilitation funding is nearly ignored.