Eldest's school doesn't do a French exchange, and she's starting French in September. No hurry obviously but she has mentioned us arranging our own exchange (a bit of a google shows various options are possible). She had the idea because another boy on her bus had what appeared to be an exchange student with him at the end of term (they were speaking French together) and she likes the idea of an exchange.
DD is already bilingual, so we are hopeful she will do well with learning more languages, but we have no personal links to France and its almost 30 years since I last had a French lesson!
Are language exchanges beneficial? Not really worrying about exam grades but about actually learning the language - would you bother arranging an exchange yourself? It will almost certainly be expensive and quite a lot of hassle, so would need to have a high likelyhood of leading to much improved French, as well as being a good experience!