Several unnamed publications seem to be in the business of providing high school students and their parents with information on colleges that is not only completely irrelevant and useless, but also misleading.
The selfsame publications will drone on and on about how the average ratio 30:1 at school A is much better than the average 6000:1 at school B, because the professor will provide more individualized attention. PLEASE! The two are completely unrelated!
The statement relies on several assumptions:
Rightfully you, the paying high school students and parents should be able to believe those assumptions. Unfortunately, belief and reality can be two entirely different things.
At many 'fine' institutions, particularly Carnegie classified 'RESEARCH UNIVERSITIES', emphasis (by the institution) is placed upon research - more appropriately, faculty & professor sponsored research. Nowhere in the equation do undergraduate students fit in. Despite paying tremendous amounts of money for college, undergraduates very rarely contribute to the 'research' that a university provides. This attitude is instilled in professorial faculty, who would rather be working on their award winning research, than teaching a class. Teaching a class consumes volumes of time - planning, grading, helping students, etc; thus ends up frowned upon by research faculty.
If recalled correctly, the primary phrase for Professors in Research Universities is "Publish or Perish" - no one concentrating on publishing has time to teach.
The other 'classes' of Universities place more emphasis on teaching from their professors, leading to more satisfied and competent undergraduate students.
If you do decide to attend a Research University, understand that you are not necessarily paying for a good education, or even an education at all. You are paying to bask in the glow of the brilliant research that takes place. On the up-side, if you do wish to do some research and get your hands wet, then those are the places to be.
Digressing, the point is to not base any decision off of class size, or the belief that teaching and education is in any way correlated to the class size. For every 'written' point of information that you read about a college, try to determine what you are meant to think from it - then try to identify if that is necessarily true. After you identify the assumptions you are making when you read college reports, you will then be able to identify the questions that you need to ask students who actually attend that University.
Above all, try before you buy. Sit in on classes - randomly. Sit in on introductory courses - these are often the worst. Sit in on upper level courses. Weigh for yourself whether the students appear to be challenged, if the professors (or T.A.s) appear to teach, and if the environment is stimulating. But don't ever believe that poor performance on the students part is the fault of the students. Most (if not all) college students are competent when they wish to be - if they are not, then they do not wish to be; there is undoubtably a reason for that.