The fifth grade science standards are broken up into four main parts: physical, life, and earth sciences, and investigation and experimentation.
Actually, investigation and experimentation is present in all the grade levels. Important much?
I've been lucky this semester to have been able to witness a science lesson once each week (with the exception of this past week, due to benchmark testing, and next week due to Veteran's day). In total, we have done one experiment and two demos.
Most of the time, the students read the textbook, answer the workbook questions, make posters and present them in groups. Which is not the most dynamic way to teach science. Nor the most effective in terms of content retention and synthesis. But we have one 55 minute time slot for science each week. And the prep for experiments is so intense, I don't even want to think of the clean up.
So of course, it doesn't seem unreasonable that most 5th graders score below basic in science. They don't receive all that much background on it in the year. The curriculum my current school uses has twelve chapters. My CT informs me that he's lucky to get through four of them by June.