You're right about Natalie Portman. Most of the ones I can think of (of recent starlets) who have started college never finished. Mary Kate and Ashley both dropped out. Claire Danes dropped out (she's not really a party girl though), Anne Hathaway left halfway through (again, not really a party girl). I think once you get used to Hollywood, be it the scene or the actual making of movies, it is hard to switch back to the academic world. Hollywood can be very attractive. But you can certainly not finish college and still be a credible role model, as Claire Danes and Anne Hathaway can attest to.