How long do american students live on-campus for?

–I posted it in the wrong section, can anyone move it to College Life :)?–

Hi. I’m currently enrolled at a British university and I’m thinking of applying for an exchange program in the US for next year.

Many of the partner universities guarantee on-campus accommodation for exchange students. In the UK, though, it’s very common to move out of dorms after the first year and look for private housing with a bunch of other people. As I’m gonna be 21 by the time I start my second year, I wouldn’t really fancy living with all 17-18 year olds.

So, do upperclassmen live on-campus too? Or is it like in the UK, where it’s 95% first years?

Thanks.