We had a boy from Japan for about 2 weeks one Summer. He was required to go on this trip, along w/ his classmates, in order to graduate from his school. He apparently hated traveling, and didn't care if her ever left Japan, and he was very shy. He did not have a great time, and neither did we, tho we tried.
A year or so later, we hosted a girl from Spain. She came as part of a program, so many of her friends were also placed in homes nearby to us. Come to find out, they were largely a bunch of spoiled kids, who came on this trip to party. She was always wanting us to drive her and her friends all over the place, at all times of day & nite, for social stuff. It was like having a bratty teenager in our hosue, and our own kids were only 3 & 6 at the time, so I was NOT prepared for that sort of behavior or driving, as I had to lug the little ones w/ me every time I drove the students. One of her friends was telling us that her family owned a CASTLE back in Spain (it was, I saw pics), as a vacation destination. You get the picture. These kids should have just taken their own private vacations, but I think their parents sent them on the program's trip to get them out of their hair for a while.
Needless to say, niether exchange went well for us. I'm sure there are better prograns out there, w/ kids who truly want to be here for the cultural experience & learning. Jsut be SURE to check out the program beforehand, and even get info/opinions form other families who have hosted kids from the same program in the past.
Good luck!