Wouldn't it be normal for highschoolers to show up at uni? To ask about careers and such?
It's pretty normal here at least
From the US: Usually only on scheduled tours, and never unaccompanied anywhere on the university campus.
However, the community college 10 minutes away shared space with a local high school, so there'd be high school students all over there.
ETA: It isn't that high schoolers aren't allowed or would be apprehended on the university campus. They're just, ya know, never there. It is a public space that anyone can wander around, after all.