What are the challenges of teaching elementary school science?

I am finishing up my education and will be teaching next fall. I am wondering what challenges there are to teaching science in elementary school. This subject scares me more than any other. Please help!

I think for many elementary teachers in the US, the big challenge is getting to actually teach science. Sadly, much of it is being pushed out of the way by greater emphasis on improving test scores in reading and math.

Another challenge is simply the setting up of the hands-on activities and the cleaning up. Hand-in-hand with all of that is safety issues.

Assessment can be a big challenge when doing hands-on science activities. How can you be sure all the kids got what they should have gotten out of all of that? Learning journals/lab notebooks turn out to be crucial here. They also give kids a chance to practice important skills like writing, describing, and summarizing.