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.
There are endless books about what every third grader must know that use the idea that factual knowledge is the basis of the ability to read as their justification. Unfortunately, the writers of these tracts have misunderstood the cognitive science behind those statements. It is difficult to read things when you don't understand what they are about, but it does not follow from that thatthe solution is to ram that knowledge down kids' throats and then have them read. It is much more clever to have them read about what they know and to gradually increase their knowledge through stories that cause them to have to learn more in order to make the stories understandable to them.
Certain things need to be done again and again in life, but those things can be learned only in context, not as an abstraction. Different contexts must be provided in order to motivate students and to provide real world skills that will be remembered, not because they were studied and tested but because they were practicied again and again.
