I have five kids.
My wife and I were schooled in Public and DOD schools.
One of my kids is very extroverted. One is very introverted. The others are somewhere in between. (youngest is 2 months. :-)
We homeschool our children and take great interest in their lives.
By the logic that is being utilized in this discussion, all my kids should be introverted cause they are homeschooled. This proves that logic wrong in my family as well in most families I've met and read about. (Homeschooling has a huge network.)
Intro / Extro is a personality trait. Neither is wrong. Certainly either can be more effective in certain environments and learning self control is key to operate. Why people think the public school is the best or even only place to learn that is beyond me. They can't even teach our kids to read by the fifth grade. Much less the twelfth grade.