The courses I teach are how related to Electrical systems and repairs on motorcycles.  The challenges are the subject matter, which in most cases is not something physical to touch, and the resistance to allowing the topic to sink in and be retained.  The other issues are the students range from ages 17 to 70.  This creates a very challnging learning environment.  Watching the students and asking questions, seems to break the ice and get them more interested.  It is the fear of electrical in most cases.  Through time and repetition, the students do grasp the concepts and theorys.  It is always a challenge.