Many colleges don’t offer as much flexibility as they appear to on paper. Certainly most of not all colleges have an add-drop period, but that doesn’t tell you how difficult it may be to add classes that you didn’t secure during pre-registration. Letting students “audition” classes is risky for colleges that may prefer to lock students into classes with less-desirable instructors.
When my daughter started at Rice, students there were allowed to overload in preregistration, which at least allowed them to start out with one extra class and then decide which one to drop. This privilege was rescinded during my daughter’s time there; and while my daughter’s class was grandfathered under the old policy, those affected were understandably NOT happy. Sure, you can change classes during the add period IF you can get the class you want to switch to, but that’s difficult with many popular classes at many if not most schools. You can show up to a full class and make your case to be added; the receptivity to this strategy varies by school as well as by individual instructor. Yale’s system is quite different in that everyone just shows up, attends as many classes as they want, and “sorts” themselves into the ones they want to take. I don’t fully understand how they make it work as compared to the far more coercive and scarcity-driven systems at the vast majority of colleges.
The “how hard is it to get the classes you want” question is an important one to ask when comparing colleges. At some high-competition-for-resources schools, this is a major issue that impacts not only the quality of education but the ability to graduate on time. This is one reason why Regents status at the UC’s is such a big deal - Regents Scholars get priority registration, ahead of athletes, who are in turn ahead of the “general population.” Prospective students at many schools often underestimate the value of priority registration conferred by honors colleges/programs. It’s extremely frustrating to spend such large sums of money on an education only to end up struggling to get the classes you want and need. It doesn’t need to be as flexible a system as Yale’s, but you do need to be able to actually access what you’re paying for.