They still almost certainly live at home and I imagine there’s an expectation from their parents to finish high school. There’s definitely a big line between being a crappy student doing the bare minimum vs dropping out.
I don't get it. At age 15 I had curfew, but could generally come and go as I pleased. At age 17 I was at times left alone at home for a few nights. This was all normal in my teenage years in my corner of the world.
Why would high school need to function as a daycare? The teachers would definitely rather not have to deal with this on top of the usual responsibilities.