Again we can never know the exact reasons or what each individuals situation is, but I believe the schools you mentioned have large part-time programs. Many part-time students go to further their already existing career, seeking an educational challenge, or for any number of reasons that may not be specifcially guided to obtain a typical attorney job. I personally never think that is a good idea, but part-time law school is on the rise and I am not even sure it existed 20 years ago. I would imagine many part-timers stay in their old careers that didn't require a law license.
So part-timing could be one factor in thse numbers and a reason for the disparity between higher ranked schools. I did a cursory look and noticed Yale, Harvard, Stanford, UCLA, and Boalt did not offer part-time programs.
Then at a school like Cooley the majority of studnets are part timers 1,289 part timers compared to 221 Full-Timers. http://www.lsac.org/LSACResources/Publications/2011OG/aba1796.pdf
I imagine most part-timers already have a career that did not require a law license and did not feel secure enough to leave their old job to go law school. If they kept that job for four years odds are they will not leave it to start a new career from scratch. This may be a significant factor in the numbers you.
My theory could be 100% wrong, but I would like to see how the numbers played out for full-timers v. part timers at these schools. If any info like that exists feel to free post for my own curiousity.
As an aside I personally never think part-time law school is a good idea. You should go all in or avoid law school. Part-timing is going to be an extra year of your life and if you weren't secure enough to leave your old job odds are you won't be anymore secure four years later. You also will not have any desire start a new career from scratch, and then you paid 100k to be in the same spot. Furthermore, odds are you will finish near the bottom of your class if you were working all through law school and get no legal experience because you will be in your old position.
Granted part-timing does work for some and I am nothing more than an anonymous internet poster that didn't do part-time law school, but I think part-timing is the culprit behind the poor employment numbers at many schools. The reason is for the facts I mentioned above again just a theory, but it makes sense to me.
I am currently part-time at night and my sole reason for working is to keep my debt as low as possible. The same is true for many of the other part-timers at my school. It really has nothing to do with being afraid to go all in and more to do with having 150K in debt. I will cut my debt in half by working and saving and to be honest, one year more is really not much longer. Most of the students have families and are older. They are generally, (at least at my school), not young people just out of college.
I think the main reason part-time law school wasn't done twenty years ago is because law school wasn't nearly as expensive as it is today. Sure lawyers had debt, but I remember reading an article that talked about how the increase in ABA tuitions had more than doubled itself over a certain number years. If I can find the article, then I'll post it. Most of us plan on quitting our jobs after our second or third year to get experience as interns, etc. Some of us already have jobs waiting for us when we graduate.
A prosecutor came to speak at our school and discussed part-time versus full time. It's not even something they consider on job applications. They mainly look at grades, internships etc. Although part-timers can't do internships traditionally, most of them can find internships through their legal departments at work, or if they quit their jobs their last year of school. One of my professors suggested that to us. He is a prosecutor in California, worked for the first three years, and did externships, etc. his last year before landing his job.
Just wanted to clarify, because I think part-time is actually a smarter way to go than full-time. Even if you work and can't afford to pay some of your tuition, you will still save on books and living expenses. With less debt, a person has more options if they don't get a job in six months because they'll have less debt and some type of work experience - even if it's not necessarily legal experience. While full-time has traditionally been the norm, I think part-time will become more and more popular as ABA schools become more expensive. Fiscally, it seems to make more sense - at least to me.