We hosted a French girl who clearly came from quite a difficult background, which seemed to make her teachers even more determined that she should take part. (Prior to the visit I received a series of odd and demanding messages from the mother, which seemed to be part of a known pattern. The girl herself was lovely but there were a whole series of things she had never done or been allowed to do, like go on a boat or eat in a restaurant.) The French school arranged, without us asking, for DD to stay with a
lovely family with a child in a different year who was not part of the exchange.
Whilst talking to my daughters school, it became clear that this sort of thing was not unknown. One poor German boy apparently broke down in tears and told his English family they were lovely. His own father was prone to binge drinking and could be awful, and he was worried that this might happen when the English boy as staying. The problem was finessed. Teachers are available and able to sort problems quickly.
I think it is a good experience for a teenager to be host as well as going on an exchange. It is a chance to think about someone else, what they might like etc. If you can find some short term space or negotiate that the exchange stays somewhere else but your DC is involved in the hosting, so consider it.
I know a couple, now in their 80s, who met on a school exchange. He is French, she English. That exchange worked!