There are several approaches to the exchange of knowledge, but the most commonly used (not necessarily always the best) is the lecture method. Given that, the lecture can be effective or a disaster depending upon the presentation. There are several aspects of lectures that warrant attention:
Issues: Small classes v. Large Classes
Different approaches may work better for large or small classes. One of the major challenges in large classes is getting the students involved in discussion etc. (active learning versus passive learning). Also, as class size grows, it is more difficult to coordinate projects, grade assignments, etc.. A nice summary of the literature on the class size issue will be given as a class handout (written by Ludy T. Benjamin).
Other Methods of Teaching