I live in the US. We moved to a different state (I know it is not quite the same as moving abroad) when I was 14, and at that age I never event thought that I could ask to stay with my grandparents. I was not legally an adult. So I went wherever my family went. When I turned 18, I moved back the state where we originally lived.
As I said, there are many factors to consider, including the impact on his friends and schooling. Personally, I don't even remember what I was doing when I was 15, and I hardly talk to any friends I had at that age.