Hi Tanya!
I have 4 school-aged children (7th, 6th, 4th, 1st) and a 3 year old. We usually school from 8-10:30, have outside P.E. (bike riding, scootering, games, hike) for 30-45 minutes, school from 11-1PM, break from 1-2:30PM for lunch and quiet time, and finish up school from 2:30-4:30. My 1st grader is finished with everything but history/science by lunchtime. So the actual time I am teaching is roughly 6.5 hours a day. Not everyone is actively working that whole time (except maybe the 7th grader).
We do memory work (IEW Poetry/Scripture), Math (Dociani Pre-Alg/ SM 6B/4B/2A), Latin (Latin for the New Millenium, LfC A), Classical Writing (Maxim/Homer B/Aesop A), SOTW 3 w/ Activities & reading, Teaching Co's High School Am. History, & My World Science, with a smattering of other things in there.
On average, I would say the actual time working breaks down like this:
1st grader: 2 hours
4th grader: 4 hours
6th grader: 5 hours (she's a super-fast worker)
7th grader: 6.5 hours
Hope that helps,