Awhile ago on Pharyngula it was brought up scientists do a poor job of outreaching to the public in general and in the course of discussing this that professors are not trained educators. Teaching is an art that requires a certain set of skills to go with a passion to teach and tremendous amounts of effort.
To become a life science professor, first you go to graduate school (well after years of schooling leading to an undergraduate degree). Your first year you take classes and rotate in various labs. After that you join a lab, pass qualifying exams, start your research and usually serve as a teaching assistant for a semester. Usually, you then TA one more semester and then do research until your research/thesis committee decides you have done enough to merit receiving a PhD. TAing is a requirement that is checked off. At SnobU, I took a "class" workshops to help me TA and become a better teacher. Who taught it? Other grad students who were teaching fellows for Grad Student center at SnobU. In other words, their training was not much beyond mine. They tried their best but in many respects it is the blind leading the blind. When TAing, based on my experience, professors do not provide much guidance. I gave a lecture, what advice did I get afterwards? Basically none.
After grad school, people post-doc where they do more research and try to make a name for themselves. Usually no teaching. One might supervise grad students/undergraduates but this typically ends up with the Post-Doc using them as an extra pair of hands because the pressure is to churn out data to in turn, turn out papers. Based on your research and potential to do research (i.e. get grants that bring dollars to the school), you get a position as a junior faculty member. Then you apply for grants, get a lab up and running, serve on committees, do research, write papers and as throw-in teach classes. Teaching is to be done but not at the expense of getting papers out and obtaining grants. Over time, you do less research and teaching and more of the administrative work. Tenure is primarily based on research not teaching. Throughout the process, people are selected mostly for their potential/ability to do research whereas teaching is viewed as a distraction from that goal.
Now some professors are able to do it all. Usually because they love teaching and value it. Those that really love teaching become professors at small liberal arts colleges where they can practice their art in an environment in which they are rewarded for teaching.
The upshot is though that most life science professors can not teach. They were never taught and have a hard time explaining their research to a larger audience. With the current attacks upon science, this is a major problem because scientists can not defend themselves because they lack the tools necessary. The poor teaching also means groups of students leave college without understanding what science is and basic scientific knowledge. Not to mention the numbers of students who run away from the sciences while in college.
On the other extreme, a significant percentage of middle and high school teachers are not properly trained in the sciences that they are teaching and/or are not given the resources they need to teach science and keep themselves current. (Another rant, why is it usually in high school, 2 years of science is required whereas 4 years of each English & Social Studies are required).
In the end how can we expect students to value learning from teachers when those at the highest levels of our education system do not value teaching?