I feel that parents who chose to homeschool do so because: they want to shelter their kids from the "world", they are overly protective and paranoid,or they want their children's schedule to fit their own.
Sorry about your bad experience, but your blanket statements seem designed to deliberately inflame and put people on the defensive.
How about the parents feel they can do a better job than their local public school and/or they can't afford private school? How about their child WANTS to be in an environment where they get to choose to learn the things that are the most important and enjoyable to them, the things they really need to know to function in a well-adjusted, happy way once they reach adulthood?
My daughter knew all of her letters/numbers at 18 months, was reading at 4, coming to work with me from the age of 7 where she learned Quark, Illustrator and Photoshop and used those skills to create her own business cards and flyers for her "travel agency", taking incredible photographs starting around the age of 10 (which was when her creative writing skills really took off), playing guitar and piano at 11, cooking gourmet vegan food at 14 which was also when she had her first singing gig, etc. I could go on but I have to check her biology and French homework before she goes to hang out at the local coffee shop with her artist friends. (Yes, she has friends.)
To answer the original question: Calvert and now American School. She will be graduating from high school at 16 and plans to attend a visual arts college in NYC.