what does the phrase "on the college circuit" mean?

It's someone, or a group, that travel from college to college recruiting students for various purposes.

Going from college to college trying to sign up graduating students for whatever it is he's recruiting for. Sometimes, I suppose, it might be a formal program: you do college A, then B, then C, every year in the same order. Other times and other recruiters, it might be more informal, depending on if the schools schedule job fairs or things like that differently every year. There was just an anthropological study published about investment bank job recruiters who only recruited students from Harvard and Princeton, two schools always highest-rated.

I'd also say "ON a cool spring day", and it's "campus" not "camous"

Thank you so much

thank you for your detailed reply!