As I have said before our children are kept close to us from the start. It has been at times difficult in the face of  "the norm".  And  family relations are not always a part of the team. The socialization question or issue is the most frequently used. The human is not social in only a school/ institutional setting. We are not meant to be surrounded by only our age group. This notion is insane. In normal everyday life, we are in contact with all age groups. The peer group need not be age oriented only. We ,as adults , recognize that our peer group is not always  our age group. So why impose this on children. 

Socialization happens. In some cases it may need to be "taught" but if one is interactive with society on any level it will happen.