This might be a half-baked idea, but what about the dual-credit/high school students that take classes at Elsewhere UN (If there are any). Them not knowing about the fair folk at first, but quickly learning and keeping iron, salt, and any other protective measures with them everywhere they go (including their home school). Their friends asking about their weird habits, and them giving their friends iron jewelry and insisting that they always wear it "just because". (maybe more on this later.)
Oh wait yes fantastic! And like two thirds of the time it’s not even because they learn about the Fair Folk, it’s just taking part in this weird school tradition thing that all the university students seem so intense about. Some of the kids going home do so armed and more aware of what’s waiting in the shadows, wherever they end up. But others just think it’s a Cool College Thing College Kids Do. And here’s the thing: they’ll forget the longer they spend away. The kids who end up going to non-EU schools after high school will forget why they have these habits, long after they’ve realised that in fact EU had some pretty goddamn weird traditions.