Unfortunately, discovery can take a very long time -- much longer than a course lasts. It took the leading classical economists a hundred years of wrestling with different concepts of supply and demand -- often misunderstanding each other -- before finally arriving at mutually understood concepts that can now be taught to students in the first week of introductory economics.
The Chronicle of Higher Education reported that the discovery learning professor sometimes seemed to be the one doing most of the work in the class, "bringing the students' sometimes fumbling answers back to economic principles."
This course's main focus is said to be not on mastering the principles of economics, but being able to "dialog" and discuss "shades of gray." With such mushy goals and criteria, hard evidence is unlikely to rear its ugly head and spoil the pretty vision of discovery learning.
Discovery learning may not serve the interests of the students, but it may well serve the ego of its advocate. Education may be the only field of human endeavor where experiments always seem to succeed -- as judged by their advocates.
By contrast, the third method of teaching introductory economics, in lectures by Professor Donald Boudreaux of George Mason University, tests the students with objective questions -- which means that it is also producing a test of whether this traditional way of teaching actually works. Apparently it does.
The Chronicle of Higher Education also reported on the students. The feckless behavior of today's students in all three courses makes me glad that I left the classroom long ago, and do my teaching today solely through my writings.