NS highlights most of the big differences. Another I would add is this: TIME.
Even non-teachers get acclimated to the 7 hour day. I don't know a single hs'er who actually KEEPS that 7 hour day, although many start off with the idea of "I'm going to do X number of hours a day". The school day in away-school is dictated in large part by how long it takes to teach THIRTY kids "x", plus regulated breaks for both the kids' and teachers' sanity.
HS'ing you get to set your own schedule, which is SUPER hard for many prior teachers to adjust to (while others just kind of giggle and revel in it). For me it was/is hard. Some days we do school from breakfast to bedtime, just because we're having fun. Other days we don't do a lick. More often we do a couple hours, but they're sandwiched in between things like climbing trees, sports, playdates, dance, videogames, visits with family, movie marathons, lazy summer swimming, snowboarding, fieldtrips... you name it. I should KNOW better (by now 3 years in), but winter and summer are our most "productive" and those are the seasons we spend the LEAST amount of time "schooling". (In the winter we snowboard, and in the summer we do water schtuff). We spend maybe 2 hours tops doing school, yet we invariably get through at least a year's worth of work in 3 months. Doing 2 hours a day.
The argument I play out in my head over and over is the whole "consistency, rabbit & the hare, regulated, discipline" thing (gosh I'm eloquent tonight :P) v. the actual "results from the experiment". The results being 4 fold:
1) What we're doing is obviously working, and working well. (we're several years ahead in most areas, except for some "fun" ones that we just keep going deeper into, instead of progressing)
2) He's 6/7/8 years old (depending on which year I'm berating myself). Discipline and rigor he'll learn naturally over time. I don't have to grind it in young, it's a natural byproduct of goal setting and achievement and with interacting with the world around us. I myself had NO discipline in my studies until college, because I was under the misapprehension that school was for learning instead of preforming (result ='d near perfect SATs -don't let my atrocious grammar mislead here- and flunking out of HS). I'll teach him how to play the academic game (which is a durn useful skill, once I finally got over my own self important hubris, I did actually learn how to do it), but it's not the only thing worth learning. So why stifle learning unnecessarily? If he can get the work done in 1/10th the time, why drag it out purely for appearances? Conversely, if he's struggling, why make something difficult even harder by insisting that something painfully difficult *must* take place for a certain amount of time at a certain time? Same token to both, he's in outside classes so he's learning to interact in a classroom setting as well as at home. So why try and make school at home mimic a system (away-school) that has an entirely different equation as it's basis for the solutions implemented?
3) Observationally; most our nation's (and most of the world's) best thinkers and most successful individuals don't structure their lives "normally". They tend not to punch clocks, but instead derive systems that work the best for THEM. So by not following a strict school "schedule" / time, but instead doing what works best at the time, learning to improvise and adapt, learning to incorporate daily opportunity and become flexible... not such a terrible standard to rise to.
4) My mantra: "Love of learning." & "We've got time". It's hard for me not to "teach to the test". I've a visual person who likes easily recognizable progress and achievement. So I periodically have to do a reality check. This is ELEMENTARY school. His brain is NOT working at full capacity. Each and every thing that we're learning we will be coming back to in the future. So it's "light the fire instead of fill the pail" (but I LIKE pails!), inspire a love and passion for learning, teach HOW to learn over what to learn, and RELAX. We will, after all, be doing all of this again in a few more years. Ancient Egypt will be revisited, as will Picasso, and Shakespeare, and every single aspect of science. Even maths get returned to.
So for ME, at least, the hardest thing is relaxing about the time commitment. Not only what *others* think we should be spending, but what my insecure side keeps saying we "should" be spending. Even when "should" in no way lines up with reality, much less optimal reality.