How do you manage to teach history, English, math-algebra, geometry, trig, calculus, biology, chemistry, physics, social studies, government and all the other courses I remember taking in 12 years of public school?
How do the children get tested and get a class rank?
I/they don't do trig, calculus, chemistry, and physics. If they wanted to there are online classes (over 50 different classes available) that can be taken for the class and earn the credit.
The other classes have tests built into the books that we use. They are then graded by the percentages they get from daily work and tests. There are things that books can't teach someone, only actual participation will get you the education.
There is no class ranking in the program, just GPA and basic skill scores.
Why such a sheltered life for the children?
What a bad assumption to make of my children and how they are. We/they do what we want, when we want but school has to be done first. When people tell me what smart, kind, courteous, and considerate kids I have I am very proud of how they have turned out.
I think the majority of home-schooling in the US is for religious reasons, though there are others as well no doubt.
The following by Jimmy John is a good answer
I believe that you'll find that the single most common reason for home-schooling in the U.S. is quite simple: To provide a better education for their children. Not to shelter them from society. Not to bring them up in some strict religious environment. Just to educate them better. And many parents feel that the government-run schools (AKA "public" schools) in this country have let them down. A large number of them (I'll not go as far as to say most of them) are mediocre, violent, places that teach to the lowest common denominator.
Not all things can be learned in a book. Not all tests can tell how smart a person is.