Aunt Bee, I can give you my take. There is not much hanging out between most JW high school students and non-JWs. Outside school activities are very limited, with most JWs I knew not being allowed to do anything outside of school with non-JWs. After graduation, most people go to college. If a JW doesn't go, then most kids don't want to hang out with such a "loser." And there is just not much they have in common (or the JW wouldn't be allowed to do it). Most kids have boyfriends/girlfriends in and after high school. Most JWs don't, or if they do, it's because they are planning on marrying, not just dating. Also a lot of college kids get involved in experimentation of some sort, whether it be drinking, drugs, sexuality, or whatever. Since a JW is not allowed to do so, there isn't much reason for the two to hang out. But maybe the biggest thing is that while in HS, a JW kid could be still included by others because they figure it's because of the JW's parents that they are a JW. After HS, most kids can move on and make their own decisions. Not so with JWs. Once kids assume that a JW is a JW by choice, and they learn a little about the religion - they really don't want to be preached to or be friends with someone who would let their kid die by refusing blood and will never celebrate holidays with them.
But to directly answer your question about being "allowed" association with people after high school. The simple answer would be no - they do not love Jehovah, and so would not "good association."
