There appears to me that there is a significant misalignment between the often clear interest of students regarding science topics and the often equally clear uneasiness of teachers regarding facilitating classes.
For the students, their natural curiosity is high. We parents (and now for me, grandparents) frequently face a series of questions usually including "WHY ..." from the moment the youngsters learn to say the word. Through visits to the library for books, recordings, movies, and programs, to museums for demonstrations and hands-on activities, and though programs now available on cable television, parents and families can provide sources for some of those questions. As the youngsters learn to read, they themselves can begin to find the answers themselves.
A personal example: I was invited into one of our grandchildren's classrooms. As I always do, I asked if the teacher wanted me to continue on the current topic or study or consider some topic of my choice (I prefer actually the former but follow the teacher's wishes). In this case, the teacher said they were dealing with the state standards on "the sun and moon" if I might wish to use that topic. I decided to follow the teacher's wishes - with a broadening to talk about the solar system in general to some degree. As I started my visit, I used questions to generate discussion as I typically do. When a significant number of the students began providing good information in response to those questions, AND then went further to discuss material beyond the questions, our time together went by quickly, I actually learned a few new things, and I was impressed by the students' knowledge and their willingness to share it. As I was preparing to leave, I asked the teacher if indeed she had broadened the subject beyond the sun and moon. She said she had not and also said she too was impressed. She noted this happened from time to time AS A RESULT OF THE STUDENTS ADDRESSING ON THEIR OWN THEIR CURIOSITY!
Though she did not express any apprehension about the students expanding the discussion beyond her prepared material as apparently happened with some frequency, I believe it is that apprehension that is the source of many teachers' beliefs that they are not prepared. It's probably not the preparation, I believe, for the following reason. Every teacher's education must include the science requirements for high school graduation and for the general education requirements for college graduation. The material in those required courses are far beyond the science required for facilitating elementary science classes. I believe the apprehension is associated with THE FEAR OF GETTING STUDENT QUESTIONS FOR WHICH THEY DON'T KNOW THE ANSWERS.
There is no way any teacher (myself included of course) can know every answer; DON'T WORRY ABOUT IT! Turn the question, EVEN IF THE ANSWER IS KNOWN, into an inquiry opportunity. Ask the students to use available resources to seek relevant information and then work with them to organize and understand that information to begin to approach answers. If you don't know the answer from the start, just tell them and then work together. If a student gets information at home, remind the class of the source as you include it in the search. If there is conflicting information, use it for what it is: an opportunity to explore explanations as to which is more correct. Maybe in some circumstances, either could be correct. RELAX, BE A LEARNER WITH THE STUDENTS, FACILITATE THEIR (AND MAYBE YOUR) SKILLS TO DEVELOP EXPLANATIONS, AND ALL LEARN TOGETHER.
The good news is that enabling students to actively participate in knowledge building (rather than simply acting as sponges trying to absorb information you provide) will help with their intrinsic motivation for learning, for addressing their curiosity, and for sparking their curiosity. They will be much more comfortable with open-ended inquiry projects - through which their effective learning and problem-solving skills will be further developed. They will be much more likely to engage in efforts outside of class, expanding and deepening their learning. They will be much more enthusiastics about other classes - learning to read better because they want to satisfy their curiosity, learning the math skills so they can more creatively address inquiry projects, etc.
One caution: If you are apprehensive, don't try a complete overhaul all at once. Start with a topic you are most comfortable with and try the new approaches. Do the types of information gathering and organizing ahead of time to be better prepared to facilitate those skills development. Reach out to higher education institutions near by for assistance; some at least will be supportive. Check various organization websites and blogs for answers to questions and concerns (I'm a member of the National Science Teachers Association (NSTA) elementary list serve; you will get lots of assistance from that group for your questions). Talk with high school science teachers about the possibility of HS students willing to assist you. AND ABOVE ALL, THREE THINGS: (1) continually self-assess how things are going and address items as appropriate; (2) make sure your assessment of student learning involves use of the knowledge gained as well as the skills learned; and (3) relax and enjoy yourself! It may be far from obvious at this point but I believe you will come to enjoy science class if you give it a chance.
As always, I look forward to your comments and to the further exploring of this topic together.