The marble rolling lab that I referenced in my last post could have been conducted in one class period had I provided the procedure to the students. However, my desire to have the students plan and carry out the investigation meant that this lab would require two or three days to complete.
The authors of both The Framework and the NGSS knew this when they set their vision for science education. Instead of giving teachers a large list of content to cover, they provided a shorter list of "content," allowing time for the development of process skills and for increasing depth of student understanding.
In order to accomplish this, we're going to have to take a hard look at what we are teaching. Does it align with the standards? We will have to discard some things that "we've always taught" in order to leave enough time for teaching what's actually in the standards.
So don't worry if it takes a little longer this year; just make sure what you are spending time on is actually in the standards for your grade level.