First of all, congrats on getting into one of your top choice schools, and so early! That's great news! Without knowing what's important to you, there's really no easy answer to your question. There are a few things to consider though: why is school A one of your top choices while school B is further down the list? Is school A ranked higher? Do you happen to know a lot about both schools? Have you heard not-so-great things about school B? Is school B in a location you don't care for? Basically, how did you decide where schools fall on your priority list?
When I applied last year, I didn't rank schools until after I interviewed. I attended all my interviews while trying to keep an open mind. Things like USNews ranking tend to influence how people prioritize schools before they interview, but I really don't think it should. I don't know which schools you're talking about, but for example, if you just got into Chicago (school A) and are considering whether you should attend your Drexel (school B) interview, it might be easy to say you won't likely attend Drexel even if you don't know much about the school. But if you're saying that without knowing anything about Drexel besides their ranking, you might be depriving yourself of a great opportunity. Who knows, schools B might end up surprising the heck out of you.
But if you do already know a lot about school B and school A has already thrown some nice $$ your way, then it's probably not worth the school's or your time interviewing there.