I did two exchange trips when I was of that age, one to France and one to Germany. The German one was pretty grim, but that was because my father was dying of cancer at the time so I was probably not feeling particularly open to new cultures, and even that one, I have some brilliant memories of. I am pretty sure that both did more for my language skills and general independence and confidence than any amount of classroom teaching.
Why would anyone want to formalise something so effective and undangerous, particularly when that is likely to crush the whole idea except for the most well-prepared and determined of families? And surely, the criminal records check people are already overloaded and checks are taking ages...?
I expect the next move will be CRB checks for pregnant women and their partners.