Quality of undergraduate education is hard to measure quantitatively in a way that would be needed to build nicely ordered rankings. Also, few people take the same courses at more than one school, so there are not many side by side comparisons.
http://www.usnews.com/education/best-colleges/articles/ranking-criteria-and-weights shows that the USNWR rankings are mostly based on proxy measures. Selectivity and correlated measures are 35%, wealth (of the college) related measures are 35%, reputation is 22.5%, and relative graduation rate performance is 7.5%. Only the last can really be seen as purely a treatment effect of the college, but even that can be confounded (e.g. depending on which majors students choose, or whether the college offers “gut” majors and pushes weaker students into them).