Getting It Wrong Helps Learning

An article in Scientific American, Getting It Wrong: Surprising Tips on How to Learn, reports on research that shows 

learning becomes better if conditions are arranged so that students make errors.

People remember things better, longer, if they are given very challenging tests on the material, tests at which they are bound to fail.

This learning effect occurs because generating possible (even if wrong) answers) to questions or retrieving information (even if failing to retrieve it) helps remembering more than simply studying the information.