Background:
I am a 16 year old in high school and due to various opportunities (namely being homeschooled) I have been able to take many courses at a local college. Until recently I have been taking one class per semester which means that I pop up for class and effectively disappear afterwards which reduces my contact with other students. I look much older than I am and have at times been mistaken for a 20 year old student.
Problem
Recently I began an almost full time load and have been having a little bit more interaction with students. I am not a particularly social person and am completely fine with the fact that I have zero friends and acquaintances but recently some of the students have been becoming a little too friendly (for my liking. Perfectly normal college student behavior though). I can handle the "hello how's life" style of comments/questions but a few examples of what is really awkward for me in particular are:
A few girls have come up to me and (I believe genuinely) asked me out.
I have been invited to join study groups of various sorts which are essentially social opportunities while studying
I have been invited to parties at students's houses and dorm rooms
In all three of these cases I have had no interest whatsoever in participating (along with my parents most definitely not letting me go) but the other student had no way of possibly knowing that I wasn't the average student and in the end they all turned away awkwardly and disappointed. I would like some suggestions about both these specific situations and other similar situations as to how to alert them of these facts without appearing harsh or angry and prevent any future communications in class from being awkward.
To clarify, I enjoy talking to these people and do not want to lose them as friends or make our relationship awkward while also very strongly communicating the fact that I do not have all of the freedoms of a college student.