The early findings into research on home educated children's social contacts are here which demonstrate that the assumption that home educated children are 'hidden' is laughable.
In fact the term 'home education' is a bit of a misnomer; many HE children spend a large proportion of their time out of the home: learning in the community, mixing with people of all ages. How easy is it to cram in a social life if you are restricted to 15 minutes playtime at school, or in the hour squeezed between getting home from school/homework and tea-time/bedtime?
The schools around here are currently on half term, so we are trying to arrange playdates with my children's friends who are school children; many of the school kids are booked up all week, trying to meet all these friends that they share a classroom with, but never actually get a chance to play with. And people think that home educated children have limited socialisation..?