It seems a lot of the differences listed here tend more toward the cultures of the countries where we live. Here in the US, we tend to go to the extremes.
Like basschick, I also lived in a "good middle class neighborhood" where everyone knew each other and watched out for each other's kids. Unfortunately, times have changed. The freedom that I had in the '60's and '70's are really not an option for kids today. That neighborhood/small town community thinking is disappearing, causing parents to need to be much more vigilant with their children's safety since they are on their own. I've lived in 4 different neighborhoods in 4 different states and none of them have had the same feeling of community that I had growing up. We barely know our neighbors. I do not allow my children to play outside in the front of our house unless I am there to watch them. Consequently, they play in our backyard where we are isolated from the rest of the community.
As for having to sign your children out of school, as an elementary educator I can pretty much guarantee that that has to do more with insurance than anything else. The school sytems fear that if anything happened to a child on the way to/from school that the parents would hold them liable. It sounds ridiculous, but unfortunately, its true. Not that the schools don't worry about the kids. We do, many times more than the parents. However, in today's litigious society, the school systems have to be doubly vigilant.
Kaz