High school students interested in philosophy would do best to identify schools that have strong reputations for undergraduate education first. Only then should they look into the quality of the philosophy department. Some highly ranked Ph.D. programs have good reputations for undergraduate education, like Princeton, Yale, Brown, Wash U/St. Louis, Northwestern and Rice, among many others. The larger universities (like Harvard or Michigan or Texas) tend to offer a more mixed undergraduate experience, largely due to their size. Since much of the teaching at those institutions will be done by graduate students, it pays to go to a school with a strong PhD program, since that will affect the intellectual caliber of teachers you will encounter.
Many schools that do not offer a PhD or MA in philosophy have strong, research-active philosophy faculties, for example, Amherst College, California Institute of Technology, Dartmouth College, Reed College, University of Vermont, Wellesley College, and Western Washington University, among many others. The colleges in the Claremont system (Claremont-McKenna, Pomona, Pitzer etc.) have, collectively, excellent faculty resources for philosophy students as well. Needless to say, many other good liberal arts colleges and universities that only offer a B.A. have strong philosophy faculties (i.e., faculties doing philosophical work at the research university level) and offer good undergraduate programs. In general, when looking at the philosophy department of a liberal arts college or university without a graduate program, you should look at two things.
[ul]* Does the department provide regular offerings in the history of philosophy (ancient, modern, Continental), formal logic, value theory (moral and political philosophy), and some combination of metaphysics, epistemology, philosophy of language and philosophy of mind. You will need courses in most of these areas to be adequately prepared for graduate study, not to mention to get a serious education in philosophy.
* Where did the faculty earn their Ph.D.? The majority of the faculty at any good department should have earned PhDs from well-ranked programs (as a rule of thumb, those in the top 50). If significant numbers of faculty earned their PhDs elsewhere, be wary. Some liberal arts colleges, even some nationally prominent ones (Grinnell is an example), have philosophy faculties that are now pretty far on the margins of the discipline; by contrast, some strong regional liberal arts colleges have much stronger faculties (Illinois Wesleyan and Lawrence University are examples).[/ul]