I agree that homeschooling as a general rule is best. One on one type schoolings, parents who are involved, parents who make the social aspect just as important as the educational aspect in the curriculum can have exceptional students both in the learning and in the social skills.
However, when a parent is also promoting the seperatist attitude, such as the JWs have, it does throw in a huge social issue. If a parent is lazy about the schooling due to the belief it doesn't matter anyway because the end is near, then it is a huge issue in lack of proper education. Two of my husband's cousins have had this happen to them, as we now watch their struggle as adults trying to make a living. Their non JW grandfather has a strong negative opinion about his daughter's ( lazy) homeschooling her kids. We have occasionally heard him rant about when she is not around, it then try to keep quiet as it is obviously a point of contention among them.
Of the other parents that I know who homeschool, none are certified teachers, but all of the kids are excelling in education. Several graduated early and began college early. med school, law school. One began studies at Princeton and made honors level grades. None of the kids I know have social issues. So in my experience this belief of a social disadvantage doesn't make sense. I understand there are kids out there who do have a social disadvantage. I know some kids in public schools that are socially disadvantaged, with social issues. It goes both ways.