The biggest pointer I got was that the smartest kids are not the children of people who volunteer in extracurricular activities, but rather the children of those who read to their kids and talk about issues with their children.
That makes sense to me. I will still volunteer, because I enjoy it. (I never started being a library volunteer for my son’s sake, more because I enjoy books.) Of course, I will also read and talk to my son. I think the talking is harder. Sometimes it is easier just to not say anything about critical issues rather than discuss them.