Sorry I’ve missed this thread for a few days, but Pizzagirl and Purple Titan both expressed the essential mathematical point. Large classes are, by definition, large, i.e., it takes a lot of students to fill each class. Small classes are, by definition, small, i.e., it takes few students to fill each class. So it takes a lot more small classes to fill up as much time in students’ schedules (on average and in the aggregate) as large classes. Here’s a stylized example. If you have only two categories of classes, those with 100 students (large classes) and those with 10 students (small classes), it would take 10 small classes to take up as much time in students’ schedules (on average, and in the aggregate) as each large class. That would be 91% small classes. But then if each student took, e.g., 4 classes per semester, and there were 1,000 students, you’d need 4,000 class places per semester to fill everyone’s schedule, You could accomplish this with 20 large classes (20 X 100 =2,000 class places) and 200 small classes (200 X 10 = 2,000 class places). You’d have 91% small classes, but on average each student would be taking 2 large classes (1,000 students X 2 large classes(= 2,000 class places = 20 large classes) and 2 small classes (1,000 students X 2 small classes = 2,000 class places = 200 small classes).
There’s a kind of optical illusion here. If you see that 91% of classes are small, you tend to leap to the conclusion that on average each student spends 91% of their time in small classes. But mathematically, that can’t possibly be correct. US News plays into this optical illusion by heavily rewarding schools for a high percentage of small classes (<20 in US News metrics) while de-emphasizing the percentage of large classes. But the percentage of large classes actually does much more to determine how much time students spend in large classes (again, because large classes are, by definition, large, and so on average each large class has more influence on where students spend their time than each small class). If you focus on the percentage of large classes, you’ll quickly see that most private research universities are more similar to the top publics in regard than they are to the leading LACs, which are distinguished by having small to trivial numbers of large classes.