One thing I've done this year is have science once a week (Friday am) and only do science on that day. We spend a few hours reading and doing projects etc. Prior to that we regularly skipped any science.
As for scheduling, I have a clip-board with a list of what I have to do with each child which I make up each week. This really helps me keep on track. Each child has a schedule of work they need to complete every day - just a list, no time slots. I work with them individually, starting with the youngest (6) working up to the oldest (17) in the afternoon. It takes a bit of organizing but if I don't have a list, nothing gets done!
Hth,
Sandra.