Way back before the dawn of time... okay in the mid 80s, I went to Germany for 3 weeks to stay with a family during the Easter holiday, and the girl came to stay with us for 3 weeks during the summer holiday. There was one day of organised group activities where we visited a castle and had a picnic in a park, but apart from that we were very much alone.
My dd keeps asking me if I think they are going to do an exchange trip and I can't see it happening before her GCSEs next year. But I've also been told that they only go for a week anyway and stay together in a hostel meeting only the children not staying with complete strangers in their own home. Is that what happens?