Mostly mornings around here.
My oldest tends to wake earlier than the rest so she, the baby and I will take a walk while the others and daddy are still sleeping. We use this time to talk about stuff she's learning, review spelling, whatever we have on tap. When we get home she is ready to hit the books.
My second needs mroe time to adjust to being awake, so I wait until late morning (also nap time for baby) for her.
I don't require a lot of written work, maybe an hour 3 times a week. The rest of the time is spent reading, on the computer doing school, going to co-ops, listing to music, their outside classes, etc.
I like to have their math and written work done by the time the baby wakes up from his nap and I like having the afternoons free for their dance/acting classes and playing.