If they are basing their books in the world as we know it: For major landmarks, if it's set in present day and not some sort of alternate timeline, they keep it the same. Major landmarks include freeways, highways, places of interest, etc. For small things like stores or someone's house it's generally made up. Of course, it all depends how intimate the author is with the area they're writing about (i.e. if they're basing the story in an area they grew up in as a child.
If you're that curious, go google the name of the school and see if a website turns up.