In my view almost all teachers want to give students new experience in their life and travel to another country is no exception. It can give them a new outlook on life, could teach them how this world organized, it would be important things in their lifetime.
Firstly, when students arrived in new country, they want to see everything and will not want to have study, and we can understand them, it is amazing opportunity to look at the culture of another country, their folklore, food and tradition, but they are sent there only because they need to study, it is main idea of international exchange visits. First plus is interaction with other teenagers, after this, when they come back to own homeland, they will try to improve methods of study, if student like this experience, in future it can give them reason to come back to this country and start work/study, live here.
Secondly, there are too many advantages, disadvantages cannot compete with them. One of the biggest disadvantages is financial burden to many students, because visit to another country it is not easy and not cheapy to have that (if the school does not bear all the costs), it can also give an incentive to study more, if they want to live here in the future. Probably if schools frequently do this, students could have more enthusiasms to study.
In conclusion, I think that it is right to give teenagers chance to see something new in their schooltime, it can give them unforgettable memories about teenage years.