We do most of our formal academic work in the morning. We start between 8:00 and 9:00 a.m. and cover a core of subjects M-Th (dd8: reading, composition, memorization, math, German, Latin, music, scriptures, spelling, and exercise; dd6: reading, copywork, memorization, math, music, and scriptures). Depending on what supplemental public school programs they have that day, we add history, science, PE, field trips (ideally on Fridays), and art as they fit into the week. Most days we finish with our own formal academic work by 11:30 a.m., at which time we eat lunch. Our children read and engage in other learning activities during much of what I characterize to them as their "free time". They often play with the learning games and kits I pick up at thrift stores and curriculum sales. I even found dd3 playing with the science kit on mineral hardness last week (I'd gotten it for free, so I didn't mind that she basically ruined the kit). Also, because their father (not a German) has a degree in German teaching and speaks only German to them, all of their time interacting with him is essentially German language instruction. Colorado's homeschool law requires 172 days with an average of 4 hours of instruction per day, and I think our school-age children are learning for much more than 4 hours a day because so much of what they consider "fun" or just normal life also teaches them "academic" material.
Thanks to both our family's approach to education and the ability to homeschool, our children treat their education as a constant in their lives, not just something done in a building for a few hours five days a week. I know it's possible to have children go to school full-time and also teach them to always be learning no matter where they are, but it's hard to deny that even the most academically-inclined children sometimes view being in school as a little like serving time in jail. In addition, children often pick up from less academically-inclined peers a feeling that they shouldn't have to learn anything once they are released at the end of the school day. Life, the world, and the lessons both have to teach us don't care about arbitrary school schedules.