Going thru the college research with my d the past year, this question came up for her too. We found that there are higher attrition rates at the 0-6 schools but, from the actual students we talked to, it's not because kids were being randomly "weeded" out. Some kids don't really know what they're getting into with pharmacy, but thought it would be a good field to get into and got accepted. Some sailed through hs with great grades but never had to develop good study habits, which creates alot of stress for them in college because they get overly worked up with a "poor" grade of C and don't know how to focus/time manage effectively. Some just discover the school is not a good fit for them and they're unhappy with life there. Like every other college/major, it pays to do your research first and choose carefully.
One thing we did look at, in addition to the "feel" she has of the school, is the support they offer students. Are profs teaching classes or TA's? Are profs easily available = office hours, email, etc? Does the school have tutoring available? If you ask these types of questions, you'll usually get alot of info on how committed they are to helping students be successful.
If you're looking for a general way to compare, you might ask them how many start the program vs. how many progress to P1 vs. how many graduate.
I don't know much about STLCOP, but Butler's program is looking more like a 2+4 with a 3.0 cum, 55% PCAT, etc. required to progress. They do have a forum on their website where you can talk with pharm students.
