I am exactly there right now- four years into a relationship, only 19. We will move to the same country together to continue our studies. It is very hard work- but it all depends on what you want.
Feel free to message me if you need some advice.
I'm perhaps not the best person to answer this - I just seperated from my high school sweetheart after 12 years. We went to an international school together and we both decided to attend college in the country where we met. We went to different colleges, but being in the same country we remained together, eventually married etc. I also know several other international school couples that made it work in the long term - some having lived in seperate countries for the first year or two. If your relationship is strong enough it will work out - and if it's not, then please believe that's okay too. Speaking more than 10 years after graduating - you have a lot more growing to do as individuals, and while it's comforting to do that together, sometimes it's just not possible. Don't throw it away needlessly - it does work if it's right, and you end up with someone who shares the experience of a very unique upbringing. But don't hold on our of fear either.
I hesitate to say accept the relationship for what it was and move on (high school is a tad young), but i've seen people make it through together. It wouldn't hurt to keep the connection going via email and phone calls. If its meant to be, you'll get to visit once in a while and who knows? But honestly, i wouldn't hold my breath. You could have a great friendship to hold on to over the years though, and when you're ready to go traveling, you'll always have a good friend who'd be happy to see you.