I don't know what language your kid wants to work on, you might look at but AUP (American University of Paris). They offer summer and possibly school-year classes that pretty much anyone can take. I did it for college credit, but there were a bunch of random people in the class as well -- models, expat spouses, people with one-year visas, etc.

It needs to be approved by the Department of Education. There’s a list.

You can google a list of eligible institutions abroad. I don’t think it will include private language schools.

My kid graduated from college, but has money remaining in the 529. She would like to improve her language skills by studying abroad. Does anyone know how we can use 529 money for a private study abroad program? I say private because the traditional study abroad programs through universities seem to be limited to undergrads and I'm not sure they would allow a recent grad to participate.