I just started my first semester of an ADN program. My school admits 40 students each fall, and 5 have already dropped out of the program. The percentage that pass the NCLEX is pretty high. I think the 2006 grads had 95% or 97% pass. The average NCLEX passing rate for previous years is about 90-95%.
At my school, you must make an average of 78% to pass the course. The grade is comprised of unit exams, comprehensive final, homework, quizzes, etc. Before the homework, quizzes and other grades are averaged in you must score a 78% on the unit exams and final. And you have to get a satisfactory in clinical.