I left home at 17yo.
Being in France, I was one year ahead so went to Uni at 17yo, as a minor.
There was also the added issue that ,y parents were overseas so I arrived in a what looked like a foreign country, on my own. I didn't see my parents for a whole year again.
So I wasn't so far from the case you are describing. I was certainly 'still a child that needed supervision'... riiiight.
If you are in France, you will know that actually that sort of situation isnt unusual.
The issue here isn't with the school nor with the girl but with the parents. They took a decision it's what the best interest of the dd in mind. As it happens, it was perhaps not the best choice for their dd. It might well have been for another teenager.
What is missing here is the follow and the review from the parents to see how their dd was doing. To check if she was having parties after parties etc....
As for the other teenagers, sorry but the parents weren't fooled. The other students KNEW she was on her own after going to her flat. They KNEW. And they choose not toothwir parents. Their parents also choose to 'let them go out to her house' even though there was clearly not studying going on.
The failure there isn't with the school. The school role isn't to baby teenagers. It's to teach them.
The role of the parents is to check on their teenagers to see if they are doing well and if they re not being led astray (not intentionally but because let's face it, having a party will always be more fun than doing homework).
It was also the role of the parents to check even more closely on their dd as she was away from home on her own.