In the past four years I've heard many different variations of this question. At first I used to get annoyed but now I have to laugh. By sending your kids to school, does that mean that parents are outsourcing how to learn communication, social cues, emotional iq etc? I agree that school is a great place where these skills can be challenged but not necessarily developed or cultivated. I do agree that being able to work in groups with other children can create an environment where collaboration, compromise, and other similar skills can be refined.
Contrary to some belief, just because we homeschool does not mean we have our children all day in the house without letting them leave to see daylight or other people. It's actually that we can engineer their social experience by picking what activities and classes that spark their interest, and we can cut out all the other garbage that won't serve them. Within the context of outsourcing these classes and playing with friends at the park, sports, or other extra curricular activities, our kids have plenty of opportunities to practice these social skills.