@Ynotgo : Yes, basically a set of clusters along the line. But then the selectivity would more so be based upon GPA and scores since admit rate is tricky (like Chicago had a self-selected/niche pool of applicants before). Also, I feel as if you would have to do this before or after a certain time period because some schools are kind of frozen in time for their curriculum and rigor and some aren’t. Whether you are talking the super elite, elite, competitive, average, and not so competitive clusters. Within each cluster, it seems to just vary by department or institutional goals. Lately the undergraduate curriculum has been the last thing on the mind of most depts and schools. Also, today favors freedom and choice for the consumer, I mean student. So many (even elite) schools with much more rigorous and stringent gen. eds did away with them and substituted for a much more watered down ‘a la carte’ version.
As a result, students at schools much more academically rigorous on average have greater choice on whether to engage that rigor. I would argue, my alma mater, Emory, was more rigorous before it axed the old gen. ed requirements (which looked more like a core because there were a very minimal number of courses per requirement) and generally before the recession. After the recession, electives in STEM departments dried up in comparison to before and I think the funding for the scattering of curriculum innovations was badly effected (many of these interesting electives that had a lot of rigor were funded by say NSF or HHMI STEM education project funding). In addition, the school had honors courses in many departments much like super elite peers prior to the recession but afterwards, they are basically non-existent. You have many “lone wolves” that choose to run a STEM course like an honors course in the field, but they serve the masses as opposed to a more select crowd of students. I believe some of the other elite privates I have investigated had a similar thing going on.
I remember comparing Vanderbilt’s bioscience offerings (outside of BME, the actual bsci dept) and was quite impressed in say…2010 or so (Emory was struggling to have stable electives by then because it increased the enrollment to deal with the crisis, yet still wanted to keep comparatively small section sizes of the general biology, chemistry, and physics courses, so resources were essentially wasted down there on gateway courses), but then it seems theirs kind of diminished as well (likely for purely budgetary reasons or lack of demand). As the “recovery” happened, Emory is in pretty good shape (stable electives and a reorientation toward more quantitative options in them, implementation of primary literature discussion sections in intermediate courses). This just shows that even the economy can effect the curricula offered at these schools. Selectivity will not save you from demand and budgetary issues, elite or not. Of course at super wealthy schools like most of the super elites, the College of Arts and Letters unit can take a hit without the curricula being effected, but many or most other schools seem not to have that luxury.
There is also planning and administrative pressure: Keep in mind that not all your really elite and super elite schools were at the level they were today academically. For example, Duke appears to have added rigor (econ. is an example. Dartmouth apparently changed its economics courses to be very rigorous as well) and tiering in key areas that made them more similar to super elite peers and Ivies and currently does a lot to keeps its College curriculum fresh even in terms of gen. ed requirements and expectations. My school has a current president (who was provost) that has the agenda of truly aligning many departments curricula with research interests of the faculty and research in general, so you get cases where departments like Political Science (yes, a social science not a STEM dept) are pressured to change in a way that makes the major technically more stringent and rigorous. Like there are now intermediate courses and students are required to concentrate in a field as opposed to the going through motions a la carte way of fullfilling a polisci major. They do all the intros. pick an intermediate in the area of concentration, take necessary stats AND a methods course, and then take an upper division research based course in the field of concentration (unlike how history departments at most elites require some colloquia that have heavy writing or research component, this seems not to be a common req. for political science majors). Basically some depts make choices that make a greater share of students engage academic rigor (what I consider the good type. One that focuses on content mastery but also asks the students to be sure that they can apply it to nuanced situations or do research in a field. Basically rigor that further builds an analytical mastery as well).
They also “blackmailed” (lol) chemistry (which already had a lot of rigor at intermediate and lower division) into doing similar reforms that are much more dramatic (like a Euro system style curriculum) as a requirement to help pay for the new building that was completed like 2 years ago. Without this sort of pressure and change, many departments, will simply not keep up with their student bodies, especially if they grow more elite. You end up with a tier of elite schools that are certainly more challenging than average, but could be doing much more, especially in cases where the scores have risen even further from when they were initially considered elite (you get rising grades and relatively happy students though). It takes a lot of effort to prevent the inertia because again, professors who were just average rigor before will rarely, on their own with no incentive, start teaching more rigorously than in the past because the new crowd is great. They will just watch their grades rise and say “oh how wonderful!”.
*I am kind of curious to look more at what changes some places that were considered just elite before did to their undergraduate curricula (if anything) to make their undergraduate programs considered very or super elite today. Unfortunately, today, I cannot use current selectivity metrics as a proxy for those doing something significant because there are cases in the top 20 USNews where admit rate are at record lows and SATs are super high all the sudden, yet nothing much has happened/changed to the curricula in any departments. The admissions and communications department simply marketed itself better. I am just wondering how some of the top 10s got to where they are today other than being gifted with lots of money (some of these now have lower incoming stats than peers outside of the top 10, yet most know that the academics are generally more rigorous at that top 10 school). Was it like Chicago, where the rigor was always there and they just needed to market or play the rankings game better, or did something trigger a change in the actual undergraduate education that led to a rise that is explained more than by “greatness in, greatness out”.