However, in my opinion and especially given today's legal employment economy, this axiom may not always hold true. And when you factor in the continuing escalation of law school costs, especially at the so-called "Ivy League" schools, it is definitely "caveat emptor" (buyer beware) for prospective law students.
A good way to think about it is this. There are arguably two basic types of law students. First, there are students who go to law school because they really want to become lawyers. They love reading, debate, analysis supported with facts (as opposed to opinion), they may want to "change the world" or at least, to help people. In short, they are pretty much wired to practice law. Money is secondary to these people; their first priority is the work itself. Most of these people end up practicing law for their entire careers; in some cases well past conventional retirement age.
The other basic type of law student (and please understand, I am in no way passing judgment on these folks) seeks to go to law school for more complicated reasons. They may not be exactly sure of what they want to do for the rest of their lives. The idea of business school doesn't appeal to them. Maybe their undergraduate degree didn't exactly pan out as they had planned. Or, perhaps they simply are intrigued by the power, money and prestige that can come with a legal education. Some of these people see a law degree as a means to an end- perhaps as a business person, Wall Streeter, or academic. Many of these people practice law for a short period before moving on to their real career interests.
Which brings me to law school choice. "Local U" may be the most economically efficient choice, depending upon your career plans. Further, it may make sense if you are either of the above-mentioned two "types." For example, if you are the first type, love the law and plan to practice in your hometown, "Local U" may serve you perfectly. It will cost less and thus result in less pressure to seek a high-paying big firm job when you graduate (unfortunately, law student debt often is the primary factor in students' post-graduation employment decisions). Further, "Local U" graduates are just as qualified to sit for the bar exam as are Ivy Leaguers
As far as the quality of legal education goes, that's a pretty subjective area. One way of looking at it is to look at a school's bar exam pass rates. Arguably, there should be a correlation between pass rates and the competency of that school's graduates. Interestingly, top schools do not always have the highest pass rates (in fact, I knew of a grad from a top, top law school who worked at my first firm, who failed the Texas bar exam twice). On the other hand, top schools generally have professors with the highest academic credentials, namely that they graduated from top schools. However, the cynic in me notes that in law school, we call this a "circular proposition"- top schools are "top" because they have professors who went to the "top" schools. It kind of makes you dizzy,doesn't it?
Certainly, with a highly-ranked law school on your resume, you will likely have a broader range of career options. However, depending upon your career plans, you may not need a broad range of options (big caveat here: many twenty-somethings simply don't have career plans; I know I certainly did not.). It's sort of like using a bazooka when a .22 caliber will do.
Regardless, the point is this. Do not go into gigantic debt without at least thinking about it. Instead, give your career and future plans deep thought. Talk with a lot of people about your plans. Seek advice from a broad cross section of knowledgeable folks- your parents (stop groaning) and other relatives (even if they haven't been to law school, they are likely a bit wiser than you and their opinion is valuable), lawyers, law students, law professors and others. Most people would be more than willing to help you as you make this huge financial decision.
By the way, this analysis is the first, and arguably the most important of many analyses that you will do throughout your legal career. Good lawyers pay attention to the details. Good lawyers analyze with facts. Good lawyers seek advice when they are outside their expertise. Good lawyers prepare and prepare, in order to avoid unpleasant surprises. Your law school decision is your first opportunity to begin to "think like a lawyer."
I know it all seems pretty intimidating right now. But you can do this. It won't necessarily be easy. But then again, much of life isn't easy. That's what makes the end game worthwhile. You will become a lawyer, if you want it bad enough. I just know it.
Best wishes in your law school decision and your legal career.