I'm not suggesting that teachers never tell the truth, only that it isn't necessary to do it all the time. Since coming to one's own conclusions is mostly how we learn, the real job of a teacher is to force students to come to sensible conclusions by confronting what they already believe with stuff that is antithetical to those beliefs. A confused person has only 2 choices. Admit he is confused and doesn't care, or resolve the confusion. Resolving the confusion invloves thinking. Teachers can encourage thinking by making sure students have something confusing to think about.
Roger Schank
cognitive-science, education, learning, socratic-method, teaching