Trying to find a book...but can't remember the title?plz help?

I am trying to find a book I read in 8th grade english but for the life of me can not remember the title. What I do remember about it is it was based on 2 teenage girls who went to school together but were in diffrent clicks. The first girl is more peppy cheerleader high class type, and the second a girl named Jazz who is a little more dark, expressive, and kind of more lower class, I think.

For some reason a specific scene in the book I remember is the high class girl is riding a public bus for the first time thinking it is unsanitary or something and she is on her way to Jazz;s house. I hope this is enough info for someone out there to know which book I am talking about. Any help would be great. Thanks.