Have a look at Yabla on https://french.yabla.com/flashcards.php
They do French, Spanish, German, Italian and Mandarin Chinese.
Generally, it is a subscription site, but there are quite a few things that are accessible for free, including videos, vocab exercises etc. DS used it for Spanish and found it helpful.
Does your DS's school subscribe to any on-line language learning systems? If they do, your son may be able to sign in at home. Our school uses 'Vocab Express' and boys can access it from home using their school login details.
I found some free Japanese lessons on line the other day quite by chance, there may be something similar for European languages. Also, perhaps it's worth emailing the teachers with a question about free online resources they could recommend.