I already said this elsewhere, but I do want to reply to this comment, because it demonstrates a common mistake that may not be clear from my other comment.
If you have a given teacher, in a given classroom, with a given amount of TA help, blah blah, so that all else is equal, and then you reduce the class size, the students will do better.
The problem is that all else is far from equal in the data used in these rankings. Instructor quality drops off rapidly as you have more sections. TA help falls. The classroom may no longer be appropriate for the class, etc.
The rankings are not able to capture the effect you're talking about.
If you have a given teacher, in a given classroom, with a given amount of TA help, blah blah, so that all else is equal, and then you reduce the class size, the students will do better.
The problem is that all else is far from equal in the data used in these rankings. Instructor quality drops off rapidly as you have more sections. TA help falls. The classroom may no longer be appropriate for the class, etc.
The rankings are not able to capture the effect you're talking about.