Well, at least according to the learning theory called constructivism, that's what's supposed to happen. This theory was invented in the early 20th century, and is still taught in education schools and at professional development sessions throughout the United States. It is still greeted as a radical, new, and challenging theory, mainly because it completely defies common sense and everything most of us think of when we think about what we send out children to school for and what teachers are supposed to do.
To quote Prof. George Hein,
What is meant by constructivism? The term refers to the idea that learners construct knowledge for themselves---each learner individually (and socially) constructs meaning---as he or she learns. Constructing meaning is learning; there is no other kind. The dramatic consequences of this view are twofold;
1) we have to focus on the learner in thinking about learning (not on the subject/lesson to be taught):
2) There is no knowledge independent of the meaning attributed to experience (constructed) by the learner, or community of learners.
So if you thought that in a math classroom, the idea is that the teacher knows math and the students are there to learn it, you're wrong. If you thought that history happened and that a history teacher's job is to teach it to her students, guess again. In fact, there is really no knowledge at all. We all just kind of make it up ourselves!
This might sound ludicrous to the average person who sends children to school thinking that they're there to actually learn something, but in education circles it's taken deadly seriously. Never mind that student achievement is generally measured by standardized tests that test, guess what, knowledge. Apparently every student in a given community is supposed to spontaneously construct knowledge identical to what's on the test. If we're really serious about this constructivism stuff, then shouldn't we give every student 100%? Anybody could validly argue that just because the knowledge they constructed doesn't match the knowledge you constructed doesn't make their construction any less valid that yours, right?
Seriously, though, we teachers are consistently taught that actually teaching students things is bad. It's denigrated as "rote learning," and "drill and kill." Those things are out the window. I personally have found that when I want to teach something, or when a student wants to know something, the most efficient thing to do is just to explain what I know to them. I could spend an hour having them figure out how to play an A minor chord, or I could spend 30 seconds telling them. I'm not supposed to do that, though. Instead, I'm supposed to rely on the "prior knowledge" that students bring to class, and somehow, magically, that prior knowledge, through "facilitated" discussion, will become... new knowledge?
You can't make this s**t up, people.
Hein, George. "Constructivist Learning Theory." Institute For Inquiry. Institute for Inquiry, 1991. Web. 1 Feb 2013 <http://www.exploratorium.edu/ifi/resources/constructivistlearning.html>.