I really appreciate this post. Courses and professional goals are only half of school, so it's encouraging to hear others' experiences with integration into "academic culture."
My own background certainly isn't as extreme as some here. Although my father now has a profession-related M.S. (the first in person in either side of my family to obtain a college degree), he didn't finish school until after I entered undergrad, so I definitely have experience with growing up in a rural, blue-collar, and low-income family structure.
Even though my family has been fairly upwardly mobile (in a financial sense), I still acutely sense the lack of social or cultural capital. When I finished high school, for example, my parents were unable to offer any advice about college besides "You should go." As a consequence, I chose one school to apply to (more or less at random), and went there. It worked out alright in the end, but I still regret my ignorance of the basics -- things like "Apply to more than one school" or "Not all schools are academically equal."
Fortunately, my parents have been supportive of my graduate aspirations, even if they don't understand the academy. The opinion of my (still blue-collar, low-income) extended family is decidedly less positive; for them, grad school is a completely foreign world (and everything foreign is obviously bad, or at least not worth one's time). Mostly I deal with this by deliberately adopting a working-class persona at family gatherings. If I'm dressed like I just got back from fishing and talk like I just got back from fishing, they tend to ignore my status as a student. It's a strange, in-between space to live in, though.