Do you learn more in more challenging classes?

I used to think so, but am changing my mind.  Frankly, I'm beginning to think the fewer topics I cover, the more they actually learn.  Every year, I reduce the number of topics I cover and force my students to revisit the same type of problems over and over.  Each year, I feel like I facilitate more learning.

When you ask OK State undergraduates about their more challenging courses, challenging becomes confused with "hard", and they describe courses whose professors are bad communicators and dislike students.  If you ask them which courses they learn the most from, they are also the courses where a higher grade is easier to achieve.