As HS'ers you're not obligated to teach ANYTHING. HS'ing your children means that you are responsible for their education, not that you are responsible for teaching. Especially once you reach the higher grades (9-12), you'll find more and more HS students in college classrooms. Lower grades, as well, you'll find most of us outsource here and there. It's one of the GREAT benefits of HS'ing.
Here are some of the ways that we DON'T teach ;)
Outside classes ...(art, music, science, drama, dance, sports, etc.) These can be weekly, daily, seasonal... they can be taught at schools, theaters, labs, community centers, museums, colleges ...even for younger kids, we have our DS7 in an astronomy class at the University Observatory that's for 5-8 year olds... especially in big cities there are HUNDREDS if not thousands of options both for group and private instruction. HS'ers usually get discounts, and we can have our kids in daytime classes, and can do combinations of classes that would be impossible if they were in a regular school setting. Like 4 hours a day at the Children's Theatre, or skiing/snowboarding lessons in the morning and school in the afternoon. It's easy peasy to have our kids in an outside class or activity every day of the week... because it's only a few hours out of their day... as opposed to 8 hours of school + an activity or class. Our son does 2 sports every season in addition to 4 outside classes (not including lectures/fieldtrips/seminars/camps) that he does weekly. The schedule would be insane/impossible if all of that was on TOP of an 8 hour day away.
Camps ... (we do week long camps 4 times a year, but there are both longer and shorter camps). They're offered in every imaginable discipline & special interest. Science/ math/ robotics/ space/ languages/ sailing/ soccer/ gymnastics/ drama/ art/ dance/ etc. And that's if you don't include multi-modal camps, or scouting, etc..
Co-op Classes... These are classes taught usually by other HS parents, but a person can be hired. It's a sharing of resources
Lectures & Seminars... These can be in person, or online (http://www.ted.com/ is a good example of an online lecture option, but more and more colleges are posting their lectures online as well). These can be lectures/seminars you go to, or that you arrange with friends/family/students/specialists to have in your home. You can keep the stuff you arrange private, or open them up to other kids
Friends & Family... Use them wisely. Have a sister who's a doctor? An engineer uncle? Does you best friend speak spanish? Mom play piano? Anyone a photographer? Anyone you know work anywhere cool? Know a Rabbi who will unroll the Torah for you? A lawyer who'll tour you through the courthouse? A doctor who can show you the insides of an OR, without being under? Someone who can take you on a behind the scenes tour ANYWHERE? Nearly every person I've ever met has a job, a passion, and a hobby or 6. Since they're usually not the same as MINE, these people with their skills, loves, & knowledge become an invaluable resource.
Fieldtrips... These can be the standard trips to museums, science centers... but they can also be trips to music studios, wind tunnels, doctors offices... the places where your friends and family work... and places that you call up cold and arrange visits to. Why I have field trips in the "ways we don't teach" is because while you CAN be the person teaching your child in these places... these are also places where docents/ doctors/ videogame designers/ sound engineers/ whoever actually works there are teaching your child about what, how, and why they do what they do. :)
Online learning... There are not only gifted and regular classes taught online (with their own teachers) via schools/colleges/universities, but nearly every single major organization/ museum/ corporation/ government agency/ etc. has their own website. We regularly do virtual tours of museum exhibits halfway around the world, we came across a reference to the CIA... poof to their website. Discovery, Nat.Geo.Soc., AncientScripts.com, NOAH, there are thousands of opportunities for online learning about things that I have no clue about, much less am qualified to teach.
Prefab lesson planning. These are hugely variable... ranging from "school in a box", to individual subject curriculums, to individual lesson plans. As an example, we're doing the Genographic Project through National Geographic... that comes with, guess what?...lesson planning.
Hello College Courses... Nearly every state has a "dual enrollment" option that allows highschool kids to take college classes on campus. Most of the highschool aged HS'ers I know are at least a year into their 4 year degree. One doesn't have to be working toward a degree to take a biology or a literature class, though... one merely has to register.
There are many many more ways that WE don't teach our kids. These are merely some common examples. And, of course, we DO teach our children a lot. But whether it's a subject that we just don't know, want an expert for, want a more social environment for, or merely don't have the materials for... the wealth of educational opportunity is out there for the taking. In many ways HS'ing is like being a musical composer. We can make it as simple or as complex as we choose, & play as many parts as we like, but while we can be a one-man-band MOST of us prefer having the full orchestra at our disposal.