No. I have to know them before I feel comfortable sharing my pictures, likes, and other things with them. By "know them" I mean actually spend time talking, getting to know them, maybe hang out a couple of times. But definitely not just by knowing their name and seeing them in class everyday. Keep your info open only to people you trust.
I have no problem accepting friend requests from classmates. The majority of people on my friend's list are acquaintances from high school. I don't think it's that weird, since I don’t really take Facebook that seriously anyway. It's actually kind of interesting seeing glimpses of people's lives, even if I barely know them. If I were to only add my family members and close friends, I'd have barely anyone added, which would make Facebook seem even duller than what it already is.
I will sometimes if we at least know each other, even if we don't really speak because sometimes it can be useful if you have a question about a class and no one else you asked has the answer or is unattainable