I'm unschooling my kids. "Schooling" is about socialization and rule following, not education. In fact, the schools were never set up with education as their primary or first function. The first public elementary schools, the common schools, were in fact designed to make kids "common."
The funny thing about education in America is that people seem to think you have to have a curriculum and structure to learn. The thing is, learning takes place at every moment of every day, if you let it. Unschooling is about approaching life as a giant classroom of educational experiences. There is no need for a curriculum or a list of things you must know. There is just the child, the world, and their innate curiosity and interest (which the schools do a great job of destroying!).
I sometimes worry that my kids won't be able to compete as successfully as their peers, but my kids have always been ahead of their peers, with me doing almost nothing. We rarely do what others would consider educational activities. I rarely buy expensive "educational" toys. We have lots of books, blocks and kitchen stuff. My kids make a lot of cakes ;-)
I may add more structure when they are older, but I am a firm believer in "play" as the only requirement till they are 6 or 7.
Thus far, my results have been outstanding. My 3.5 year old would be a fluent reader if I worked with her, instead, I let her do what she just does. She knows lots of site words, and has been sounding out words since before her last bday. She is rarely interested in reading, however, and prefers for me to read to her, so I do. Her almost 2 year old brother knows most of his letters and some of their sounds, and is starting to count past 10.
We go to the Zoo a lot, and will start going to museums when my son drops his afternoon nap. But my plan is to just play hard for the next few years.
Look at Finland. They don't "school" till 7, and they are killing us on international rankings. Why? Because education isn't about workbook activities, it's about creating meaningful educational experiences.
Edited answer to Joanne: You obviously don't know what you are talking about. Kids are innately interested in EVERYTHING. In fact, my daughter is obsessed with that concept right now. If you don't expose your kids to things, they won't have many interests, but kids are innately inquisitive, and interested in enough things that any subject can be learned. Let me put it this way, say you have a kid that is only interested in baking cakes. Cooking requires lots of subjects, from chemistry to math. In fact, every single critical question you asked can be answered by "I can teach them all that, plus more, by teaching them how to bake a proper cake, you know, the good kind, from scratch, with leveling agents and measuring spoons and scales. Science, nutrition, history, reading/writing,etc. can all easily be taught by baking a cake, to say nothing of the necessary math.
On top of this innate interest that schools kills, learning by definition requires interest. If you aren't interested in something, you will not learn. You may be able to repeat a memorized answer, but that information (1) will be forgotten quickly, and (2) will never be applied to life.
Thirdly, kids run an innate program: there is a reason they all start singing around 2, start being interested in counting, etc. So much of it is biological. If you get out of their way and provide them with good experiences and good models, you will cover everything.
Research shows that true unschooled kids learn to read by 8 on average, and tend to be where their peers are or ahead of them by age 12.
Home school kids are usually 5 years ahead of their peers. I taught at a Big Ten school for a few years, and I can attest that my home school kids out wrote, thought and wrote their peers by at least 5 years, if not more, and their peers were all "AP students."
This isn't something to be scared of. Kids were unschooled until the last few centuries, and just think of all the great works of art, etc. that were created by supposed "uneducated" fools.