It stands to reason that the more time a student spends learning a subject, the better that student will perform on tests of that subject matter. A recently-released report from the National Center on Time & Learning erases any doubt about it -- where science is concerned, at least.
Five case studies look at public schools, including the Matthew J. Kuss Middle School, in Fall River, MA, where the school day was extended by 100 minutes per day beginning in the '06-'07 school year. Science learning benefited from the lengthened school day, and so did the students' performance on the science portion of the MCAS.
Supported with funding from the Noyce Foundation, the report, "The Power of More Time to Deepen Inquiry and Engagement," lists "key successful practices" identified across the five case-study schools. It concludes, "Without fundamentally restructuring the school calendar—particularly at the elementary and middle school levels—to add more learning time and prioritizing science during that time, most American students will simply not spend enough time to become either proficient in, or excited about, science."