One of the strangest places I have seen class difference -- a thing we in the contemporary socialist-democratic society would hope had vanished by now, although we know it has not -- is between teachers and students. In the university setting in particular, there are a number of interesting class relationships going on.
In general, teachers are authority figures over students, with a responsibility to those students: to teach them. Students are expected to learn from these authorities, to accumulate knowledge and to acquire the skills generally necessary for adult life. The student is a subordinate, responsible for what the teacher asks of them: they are expected to learn what the teacher is teaching. The teacher, however, is responsible for the student's knowledge: a teacher is expected not only to teach but to teach well.
So far, so good. If we were to categorize these two groups in a rudimentary fashion, we could say that the teachers were the upper and the students the lower class. The relationship between the two seems to support this: teachers are older, more knowledgeable, and have more responsibility, while students are younger, less knowledgeable, and have less responsibility. The two groups are functionally related: they are defined by their relationship to each other. The teacher teaches, the student learns. It is not unlike a traditional master-apprentice relationship.
It is also not unlike a lord-peasant relationship. Professors do have a lot of authority over their students. They control their students' future, to some extent, by providing them with knowledge x in y manner. They have the power to grade performance, to set and keep deadlines, to demand correct results. They have some authority within their department, or within the university as a whole, depending on their individual status. Those students who are registered for a given course have to do everything they can to fulfill the requirements. The professor controls them within that course, and they know it. Even if a student goes and talks to a professor about the hard time they are having with the material, or the personal issues that are making it difficult for them to concentrate, the professor may choose not to be lenient. The professor may have good or bad reasons for leniency or strictness, but the student must still abide by their policies until they are no longer a member of the course. The most a student can do is talk, and fill out the evaluation form at the end of the semester.
The class relationships get a bit more difficult when you throw graduate students into the mix. Graduate students have a strange, partial authority. They teach classes but also attend them. They have academic authority over their own students, but their advisors and professors still have ultimate academic authority over them. They are hierarchically stationed in between the two ends of the spectrum, yet are in motion from one to the other. Look, it's the rise of the middle class! Journeymen! Vassals! A mobile society! CHAOS!
It's also interesting to see how these three groups interact with each other outside the classroom. While I was an undergraduate, for instance, the closest I got to friendly relations with professors was within the strange and twisted realm of drama. Other than that, professors were essentially unreachable. I considered certain professors to be manipulative jerks, but they were still authority figures; I regarded others as very interesting and exciting people, but still authority figures. I could not get close to them, since it undermined the teacher-student relationship. What business could I have with them? And why would they be interested in me? Even as a senior, the relationship did not really change. No yeoman farmer status here.
As a graduate student, I was friends with a number of undergraduates, yet moved in a substantially different academic circle. I graded papers that my acquaintances wrote, and had to avoid becoming closer friends with several people so as to remain unbiased. As an upwardly mobile person in a higher academic class, I was not really supposed to associate casually with those students below me; I was supposed to maintain some authority, as a future professor. No one overtly mentioned this, but the expectation was still there. Still, I lived and continue to live with a house full of undergraduates: I was clearly the exception to the rule.
Those grad students who did bring their students to parties were looked at with dubious respect. I mean, you do want your students to like you, and you want them to relate to you to some extent. You want to be yourself up at the front of the classroom. It is a nice thing to do, inviting them to things; your students may be very cool people and you may very well want to get to know them outside the academic setting. But in order to teach effectively, you do need to remain in authority. This is a bit difficult to do while getting drunk with them.
Not being a professor, I cannot say for sure how professors might operate within their own peer group. I can say, however, that they tend to keep their distance from students. Whether they have different interests than many of their students (this seems probable), or whether they just feel the need to maintain their authority and responsibility, they don't really talk to undergraduates except in a professional context. There are exceptions, of course: they may be faculty advisors for some less academic activities, such as the aforementioned drama. But they largely stick to the academic side of things with undergraduates.
In contrast, professors tend to be a bit more friendly to their graduate students. They are going to operate on the same plane eventually; they may be interested in the same academic projects; they are probably close in age and personal background. In short, the two groups are allowed to have a closer relationship because the graduate student is on the way to becoming the professor. There you go: journeymen earning their way into the guild, middle class merchantry, class mobility in action!
Those people who step outside the set class boundaries may be ignored, looked askance at, judged, shunned, or, surprisingly enough, accepted. In my experience, it depends on what you do outside the boundary. For instance, teachers dating students is absolutely prohibited. Teachers having coffee with students is generally fine, however. Acceptance depends on the nature of each individual relationship; I would also assume it depends rather heavily on the individual people involved. For instance, as an undergraduate, my drama director told me the gossip about her upcoming wedding. As a graduate student, I went to my professor's house for weekly class, generally including wine. As a professor, who knows what I will do. You have to see what is best for you individually within this structure; it can be broken if you want it to be. I myself would like to hang out with a couple of my former students, now that I no longer have to grade their midterms. Hey, Angie! Hey. Give me a call and we'll have lunch.