In my class we had one student who eloped and left 1st semester, one who missed too much class due to being really sick last spring and withdrew and is doing it over again this year, 3 or 4 who transferred up to HLS, Columbia and UVA, and 1 who transferred down to WUSTL (she's from St. Louis and had personal reasons for returning). Otherwise, we pretty much convinced each other to stick around after we got through "first is the worst" semester. At some schools (Pace, for example), students who finish up in the bottom after first semester routinely fail or drop out and go find something else to do.